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Life: The Science of Biology, Ninth Edition
Sadava • Hillis • Heller • Berenbaum
Chapter 12: Inheritance, Genes, and Chromosomes
TEST FILE QUESTIONS
(By Catherine Ueckert)
Multiple Choice
1. In Kölreuter’s studies, reciprocal crosses
a. always gave identical results.
b. only involved heterozygous individuals.
c. supported the blending hypothesis of inheritance.
d. could be done only with homozygous individuals.
e. consisted of an F1 and an F2 generation.
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 237
Bloom’s Category: 1. Remembering
2. During what year did Gregor Mendel orally present his genetics project?
a. 1565
b. 1665
c. 1765
d. 1865
e. 1965
Answer: d
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 238
Bloom’s Category: 1. Remembering
3. Mendel’s research was rediscovered in the published studies of
a. de Vries.
b. Correns.
c. von Tschermak.
d. All of the above
e. None of the above
Answer: d
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 238
Bloom’s Category: 1. Remembering
4. Which of the following is not a characteristic that makes an organism suitable for
genetic studies?
a. A small number of chromosomes
b. A short generation time
c. Ease of cultivation
d. The ability to control crosses
e. The availability of a variation for traits
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 238–239
Bloom’s Category: 2. Understanding
5. If Mendel had performed experiments on cattle rather than on peas, the patterns of
inheritance would not have been easily detectable, because cattle
a. reproduce asexually.
b. have small numbers of offspring.
c. do not have observable phenotypes.
d. do not have genotypes.
e. do not have autosomes.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 238–240
Bloom’s Category: 4. Analyzing
6. A key factor that allowed Mendel to interpret the results of his breeding experiments
was that
a. the varieties of peas he used were “true-breeding.”
b. peas naturally self-pollinate.
c. peas can reproduce asexually.
d. pollination could be controlled.
e. Both a and d
Answer: e
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 239
Bloom’s Category: 2. Understanding
7. If two strains of true-breeding plants that have different alleles for a certain character
are crossed, their progeny are called
a. the P generation.
b. the F1 generation.
c. the F2 generation.
d. F1 crosses.
e. F2 progeny.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 239
Bloom’s Category: 1. Remembering
8. Which of the following methods was not used by Mendel in his study of the genetics of
the garden pea?
a. Maintenance of true-breeding lines
b. Cross-pollination
c. Microscopy
d. Production of hybrid plants
e. Quantitative analysis of results
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 239–240, 245
Bloom’s Category: 2. Understanding
9. Mendel’s crossing of spherical-seeded pea plants with wrinkled-seeded pea plants
resulted in progeny that all had spherical seeds. This indicates that the wrinkled-seed trait
is
a. codominant.
b. dominant.
c. recessive.
d. Both a and b
e. Both a and c
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 2. Understanding
10.–12. Two different groups of imaginary schmoos live in geographically separated
locations and rarely interbreed. On one occasion, a big-footed white schmoo does mate
with a small-footed brown schmoo. Three offspring result: one big-footed brown schmoo
and two small-footed brown schmoos.
10. Which statement about the inheritance of color in schmoos is most likely to be
correct?
a. Brown is dominant to white.
b. White is dominant to brown.
c. White and brown are codominant.
d. Both a and c
e. This cannot be answered without more information.
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 3. Applying
11. Which statement about the inheritance of footedness in schmoos is most likely to be
correct?
a. Big is dominant to small.
b. Small is dominant to big.
c. Big and small are codominant.
d. Both a and c
e. This cannot be answered without more information.
Answer: e
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 3. Applying
12. If big feet (B) in schmoos is dominant to small feet (b), the genotype of the big-footed
white parent schmoo with respect to the foot gene can
a. only be bb.
b. only be BB.
c. only be Bb.
d. either be bb or BB.
e. either be bb and Bb.
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 3. Applying
13. If a trait not expressed in the F1 generation reappears in the F2 generation, the
inheritance of the trait in question is an example of
a. codominance.
b. dominance and recessiveness.
c. incomplete dominance.
d. epistasis.
e. a sex-linked trait.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 2. Understanding
14. Mendel concluded that each pea has two units for each character, and each gamete
contains one unit. Mendel’s “unit” is now referred to as a(n)
a. gene.
b. character.
c. allele.
d. transcription factor.
e. None of the above
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 241
Bloom’s Category: 1. Remembering
15. The site on the chromosome occupied by a gene is called a(n)
a. allele.
b. region.
c. locus.
d. type.
e. phenotype.
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 241
Bloom’s Category: 1. Remembering
16. Which of the following statements about Mendelian genetics is false?
a. Alternative forms of genes are called alleles.
b. A locus is a gene’s location on its chromosome.
c. Only two alleles can exist for a given gene.
d. A genotype is a description of the alleles that represent an individual’s genes.
e. Individuals with the same phenotype can have different genotypes.
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 241–242
Bloom’s Category: 2. Understanding
17. A particular genetic cross in which the individual in question is crossed with an
individual known to be homozygous for a recessive trait is referred to as a
a. parental cross.
b. dihybrid cross.
c. filial generation mating.
d. reciprocal cross.
e. test cross.
Answer: e
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
18. The physical appearance of a character is called
a. the genotype.
b. the phenotype.
c. an allele.
d. a trait.
e. a gene.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
19. Different forms of a gene are called
a. traits.
b. phenotypes.
c. genotypes.
d. alleles.
e. None of the above
Answer: d
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
20. In a(n) _______ cross, genes for two different characters separate.
a. monohybrid
b. dihybrid
c. trihybrid
d. F1
e. F2
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 2. Understanding
21. In garden peas, the allele for tall plants is dominant over the allele for short plants. A
true-breeding tall plant is crossed with a short plant, and one of their offspring is test
crossed. Out of 20 offspring resulting from the test cross, about _______ should be tall.
a. 0
b. 5
c. 10
d. 15
e. 20
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 3. Applying
22. The genotype of an organism that expresses a dominant trait can be determined by
a. crossing the organism with a homozygous dominant organism.
b. crossing the organism with a heterozygous dominant organism.
c. crossing the organism with a homozygous recessive organism.
d. observing the phenotype of the progeny from any cross.
e. observing the genotype of the progeny from any cross.
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 2. Understanding
23. In mice, short hair is dominant to long hair. If a short-haired individual is crossed
with a long-haired individual and both long- and short-haired offspring result, one can
conclude that
a. the short-haired individual is homozygous.
b. the short-haired individual is heterozygous.
c. the long-haired individual is homozygous.
d. the long-haired individual is heterozygous.
e. This cannot be answered without more information.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 5. Evaluating
24. Classical albinism results from a recessive allele. Which of the following is the
expected ratio for the progeny when a normally pigmented male with an albino father has
children with an albino woman?
a. 3⁄4 normal; 1⁄4 albino
b. 3⁄4 albino; 1⁄4 normal
c. 1⁄2 normal; 1⁄2 albino
d. All normal
e. All albino
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 3. Applying
25. It has been found that at a certain locus of the human genome, 200 different alleles
exist in the population. Each person has at most _______ alleles.
a. 1
b. 2
c. 100
d. 200
e. 400
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
26. Segregation of alleles occurs
a. during gamete formation.
b. at fertilization.
c. during mitosis.
d. during the random combination of gametes to produce the F2 generation.
e. only in monohybrid crosses.
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 243
Bloom’s Category: 2. Understanding
27. Separation of the alleles of a single gene into different gametes is called
a. synapsis.
b. segregation.
c. independent assortment.
d. heterozygous separation.
e. recombination.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 243
Bloom’s Category: 2. Understanding
28. A pea plant with red flowers is test crossed, and one-half of the resulting progeny
have red flowers, while the other half has white flowers. Therefore, the genotype of the
test-crossed parent was
a. RR.
b. Rr.
c. rr.
d. either RR or Rr.
e. This cannot be answered without more information.
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 243
Bloom’s Category: 3. Applying
29. A dihybrid cross
a. results in a genotypic ratio of 2:1.
b. involves genes located on the sex chromosomes.
c. results in offspring of lower quality than that of the parents.
d. results in two different phenotypes in the F2 generation.
e. is a cross between identical double heterozygotes.
Answer: e
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 244
Bloom’s Category: 1. Remembering
30. Mendel’s dihybrid crosses
a. resulted in four different phenotypes.
b. produced recombinant phenotypes.
c. led to the formation of the law of independent assortment.
d. involved unlinked genes.
e. All of the above
Answer: e
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 244
Bloom’s Category: 2. Understanding
31. In humans, a widow’s peak is caused by a dominant allele W, and a continuous
hairline is caused by a recessive allele w. Short fingers are caused by a dominant allele S,
and long fingers are caused by a recessive allele s. Suppose a woman with a continuous
hairline and short fingers and a man with a widow’s peak and long fingers have three
children. One child has short fingers and a widow’s peak, one has long fingers and a
widow’s peak, and one has long fingers and a continuous hairline. What are the
genotypes of the parents?
a. Female wwSS; male WWss
b. Female wwSs; male Wwss
c. Female wwSs; male WWss
d. Female WwSs; male WwSs
e. None of the above
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 244
Bloom’s Category: 3. Applying
32. In dogs, phenotype A (erect ears and barking while following a scent) is caused by
dominant alleles; phenotype B (droopy ears and silent while following a scent) is caused
by recessive alleles. A dog that is homozygous for both traits of phenotype A is mated to
a dog with phenotype B. If the genes for the two traits are unlinked, which of the
following is (are) the expected F1 phenotypic ratio(s)?
a. 9:3:3:1
b. 1:1
c. 16:0
d. 1:2:1
e. None of the above
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 245
Bloom’s Category: 3. Applying
33. In cocker spaniels, black color (B) is dominant over red (b), and solid color (S) is
dominant over spotted (s). If the genes are unlinked and the offspring of BBss and bbss
individuals are mated with each other, what fraction of their offspring will be black and
spotted?
a. 1⁄16
b. 9⁄16
c. 1⁄9
d. 3⁄16
e. 3⁄4
Answer: e
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 245
Bloom’s Category: 3. Applying
34. One of the major contributions of Mendel to the study of genetics was
a. the use of statistics and probability to analyze data.
b. a complete description of the process of meiosis.
c. the understanding that phenotypes are affected by the environment.
d. the discovery that dominance is always complete.
e. the finding that heritable traits combine or blend together.
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 245
Bloom’s Category: 2. Understanding
35. Mendel performed a cross between individuals heterozygous for three different traits:
yellow versus green seeds (green is dominant), red versus white flowers (red is
dominant), and green versus yellow pods (green is dominant). What fraction of the
offspring would have been expected to have green seeds, red flowers, and green pods?
a. 27⁄64
b. 12⁄64
c. 9⁄64
d. 6⁄64
e. 3⁄64
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 3. Applying
36. Genetic mutations are
a. rare.
b. stable.
c. inherited changes in DNA.
d. random.
e. All of the above
Answer: e
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 248
Bloom’s Category: 1. Remembering
37. Tall pea plants are crossed to short, and the progeny are medium height. The F1 plants
are crossed together, but the progeny observed among the F2 have nine different size
classes. This result is best explained by
a. the existence of pleiotropic alleles.
b. incomplete dominance.
c. codominance.
d. an increased number of phenotypes due to multiple alleles.
e. epistasis.
Answer: d
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 248
Bloom’s Category: 2. Understanding
38. In the garden peas used in Mendel’s experiments, the spherical seed character (SS) is
completely dominant over the wrinkled seed character (ss). If the characters for height
were incompletely dominant, such that TT was tall, Tt was intermediate, and tt was short,
what would have resulted from crossing a spherical-seeded, short (SStt) plant to a
wrinkled-seeded, tall (ssTT) plant?
a. One-half would be smooth-seeded and intermediate height; one-half would be smoothseeded and tall.
b. All the progeny would be smooth-seeded and tall.
c. All the progeny would be smooth-seeded and short.
d. All the progeny would be smooth-seeded and intermediate in height.
e. This cannot be answered without more information.
Answer: d
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 248
Bloom’s Category: 3. Applying
39. In Netherlands dwarf rabbits, a gene showing intermediate inheritance produces three
phenotypes. Rabbits that are homozygous for one allele are small rabbits; individuals
homozygous for the other allele are deformed and die; heterozygous individuals are
dwarf. If two dwarf rabbits are mated, what proportion of their surviving offspring should
be dwarf?
a. 1⁄4
b. 1⁄3
c. 1⁄2
d. 2⁄3
e. 3⁄4
Answer: d
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 248
Bloom’s Category: 3. Applying
40. In Mendel’s experiments, if the allele for tall (T) plants was incompletely dominant
over the allele for short (t) plants, what offspring would have resulted from crossing two
Tt plants?
a. 1⁄4 tall; 1⁄2 intermediate height; 1⁄4 short
b. 1⁄2 tall; 1⁄4 intermediate height; 1⁄4 short
c. 1⁄4 tall; 1⁄4 intermediate height; 1⁄2 short
d. All tall offspring
e. All intermediate height offspring
Answer: a
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 249
Bloom’s Category: 3. Applying
41. If the same allele has two or more phenotypic effects, it is said to be
a. codominant.
b. a marker.
c. linked.
d. pleiotropic.
e. hemizygous.
Answer: d
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 1. Remembering
42. The ABO blood groups in humans are determined by a multiple allelic system in
which IA and IB are codominant and are dominant to iO. If an infant born to a type O
mother also is type O, possible genotypes for the father are
a. O or A.
b. A or B.
c. O only.
d. O, A, or B.
e. impossible to determine.
Answer: d
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 3. Applying
43. In the ABO blood type system,
a. A, B, and O are codominant.
b. A, B, and O are incompletely dominant.
c. A and B are codominant.
d. O is incompletely dominant to A and B.
e. A is dominant to B, and B is dominant to O.
Answer: c
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 2. Understanding
44. The genetic disease blue sclera is determined by an autosomal dominant allele. The
eyes of individuals with this allele have bluish sclera. These same individuals may also
suffer from fragile bones and deafness. This is an example of
a. incomplete dominance.
b. pleiotropy.
c. epistasis.
d. codominance.
e. linkage.
Answer: b
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 2. Understanding
45. A mutation at a single locus causes a change in many different characters. This an
example of a(n) _______ effect.
a. polygene
b. epigenetic
c. cytoplasmic
d. multiple negativity
e. pleiotropic
Answer: e
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 1. Remembering
46. Epistasis refers to
a. a group of genes that are close together.
b. the equal interaction of two genes so that a new phenotype is produced.
c. the expression of two genes in the same individual.
d. the linear order of genes on a chromosome.
e. the expression of one gene masking the expression of another.
Answer: e
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 1. Remembering
47. When a given trait is the result of multigene action, one of the genes may mask the
expression of one or all other genes. This phenomenon is termed
a. epistasis.
b. epigenesis.
c. dominance.
d. incomplete dominance.
e. None of the above
Answer: a
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 1. Remembering
48.–50. Agouti is a type of coat color pattern in mouse that cannot be expressed in
albinos (white mice). A non-albino, agouti mouse that is heterozygous at the albino (A)
and agouti (B) loci (AaBb) is mated to an albino mouse that is heterozygous at the agouti
locus (aaBb). Non-albino mice without the dominant agouti allele (AAbb and Aabb) are
black.
48. What percent of the progeny do you expect to be albino?
a. 0
b. 12.5
c. 37.5
d. 50
e. 100
Answer: d
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 3. Applying
49. What percent of the progeny do you expect to be agouti?
a. 0
b. 12.5
c. 37.5
d. 50
e. 100
Answer: c
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 3. Applying
50. What percent of the progeny do you expect to be black?
a. 0
b. 12.5
c. 37.5
d. 50
e. 100
Answer: b
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 3. Applying
51. A dominant allele K is necessary for normal hearing. A dominant allele M on a
different locus results in deafness no matter which other alleles are present. If a kkMm
individual is crossed with a Kkmm individual, _______ percent of the offspring will be
deaf.
a. 0
b. 25
c. 50
d. 75
e. None of the above
Answer: d
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 3. Applying
52. The blue sclera allele has 90 percent penetrance for producing blue sclera, 60 percent
penetrance for fragile bones, and 40 percent penetrance for deafness. If these probabilities
of penetrance are independent, _______ percent of individuals with the blue sclera allele
will have deafness, blue sclera, and fragile bones.
a. 22
b. 40
c. 60
d. 90
e. None of the above
Answer: a
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252
Bloom’s Category: 3. Applying
53. The complete phenotype of an organism is dependent on
a. genotype.
b. penetrance.
c. expressivity.
d. polygenes.
e. All of the above
Answer: e
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252–253
Bloom’s Category: 2. Understanding
54. Despite the law of independent assortment, when two loci are on the same
chromosome, the phenotypes of the progeny sometimes do not fit the predicted
phenotypes due to
a. translocation.
b. inversions.
c. chromatid affinities.
d. linkage.
e. reciprocal chromosomal exchanges.
Answer: d
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 253
Bloom’s Category: 2. Understanding
55. If Mendel’s crosses between spherical-seeded tall plants and wrinkled-seeded short
plants had produced many more than 1⁄16 wrinkled-seeded short plants in the F2
generation, he might have concluded that
a. the spherical seed and tall traits are linked.
b. the wrinkled seed and short traits are unlinked.
c. all traits in peas assort independently.
d. all traits in peas are linked.
e. None of the above
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 253
Bloom’s Category: 2. Understanding
56. A linkage group corresponds to
a. a group of genes on different chromosomes.
b. the linear order of centromeres on a chromosome.
c. the length of a chromosome.
d. a group of genes on the same chromosome.
e. None of the above
Answer: d
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 254
Bloom’s Category: 2. Understanding
57. When a dihybrid black, straight-winged fly is crossed to a double-recessive brown,
curly-winged fly, the frequency at which black curly-winged and brown straight-winged
flies are seen in the progeny is called the _______ frequency.
a. mutation
b. mitotic
c. meiotic
d. allele
e. recombinant
Answer: e
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 254
Bloom’s Category: 1. Remembering
58. In tomatoes, tall is dominant to short, and smooth fruits are dominant to hairy fruits.
A plant homozygous for both dominant traits is crossed with a plant homozygous for both
recessive traits. The F1 progeny are tested and crossed with the following results: 78 tall,
smooth fruits; 82 dwarf, hairy fruits; 22 tall, hairy fruits; and 18 dwarf, smooth fruits.
These data indicate that the genes are
a. on different chromosomes.
b. linked, but do not cross over.
c. linked and show 10 percent recombination.
d. linked and show 20 percent recombination.
e. linked and show 40 percent recombination.
Answer: d
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 254
Bloom’s Category: 3. Applying
59. An organism that produces either male gametes or female gametes, but not both, is
called
a. monoecious.
b. dioecious.
c. heterozygous.
d. homozygous.
e. parthenogenic.
Answer: b
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 256
Bloom’s Category: 1. Remembering
60. In guppies, fan tail is dominant to flesh tail, and rainbow color is dominant to pink. F1
female guppies are crossed with flesh-tailed, pink-colored males, and the following
progeny are observed: 401 fan-tailed, pink-colored; 399 flesh-tailed, rainbow-colored; 98
flesh-tailed, pink-colored; and 102 fan-tailed, rainbow-colored guppies. Assuming that
the F1 female guppies have both dominant alleles on one chromosome, the map distance
between these two genes is
a. 80 cM.
b. 25 cM.
c. 0.8 cM.
d. 20 cM.
e. None of the above
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 256
Bloom’s Category: 3. Applying
61 Which of the following observations support the idea that the gene controlling
maleness is located on the Y chromosome?
a. XO individuals are usually sterile, normal intelligence, female, with slight physical
abnormalities.
b. XXY individuals are sterile males with long limbs.
c. XXX individuals are normal females.
d, Some men are XX but have a small piece of the Y attached to another chromosome.
e. All of the above are observations suggesting that the gene controlling maleness is on
the Y chromosomes.
Answer: e
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 3. Applying
62. It is predictable that half of the human babies born will be male and half will be
female because
a. of the segregation of the X and Y chromosomes during male meiosis.
b. of the segregation of the X chromosomes during female meiosis.
c. all eggs contain an X chromosome.
d. Both a and b
e. Both a and c
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 2. Understanding
63. How many autosomes do humans have?
a. 23 pairs
b. 22 pairs
c. 1 pair
d. 45
e. 16
Answer: b
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 1. Remembering
64. When reciprocal crosses produce identical results, the trait is
a. sex-linked.
b. not sex-linked.
c. not autosomally inherited.
d. Both a and c
e. Both b and c
Answer: b
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 2. Understanding
65. A human male carrying an allele for a trait on the X chromosome is
a. heterozygous.
b. homozygous.
c. hemizygous.
d. monozygous.
e. holozygous.
Answer: c
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 2. Understanding
66. White eyes is a recessive sex-linked trait in fruit flies. If a white-eyed female fruit fly
is mated to a red-eyed male, their offspring should be
a. 50 percent red-eyed and 50 percent white-eyed for both sexes.
b. all white-eyed for both sexes.
c. all white-eyed males and all red-eyed females.
d. all white-eyed females and all red-eyed males.
e. 50 percent red-eyed males and 50 percent white-eyed males and all red-eyed females.
Answer: c
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 3. Applying
67. Sex in humans is determined by
a. a gene called SRY found on the Y chromosome.
b. a gene called SRY found on the X chromosome.
c. a gene called SDG found on an autosomal chromosome.
d. the simple presence or absence of a Y chromosome.
e. a gene called SDG found on the Y chromosome.
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 2. Understanding
68.–69. Cleft chin is an X-linked dominant trait. Assume that a man with a cleft chin
marries a woman with a round chin.
68. What percent of their female progeny will show the cleft chin trait?
a. 0
b. 25
c. 50
d. 75
e. 100
Answer: e
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 258–259
Bloom’s Category: 3. Applying
69. What percent of their male progeny will show the cleft chin trait?
a. 0
b. 25
c. 50
d. 75
e. 100
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 258–259
Bloom’s Category: 3. Applying
70. Very few genes have been located on the Y chromosomes. Y-linked genes include a
gene called testis-specific protein Y. A male with this gene will
a. usually pass it to his sons, but occasionally also to a daughter.
b. only pass the gene to his sons.
c. only pass the gene to his daughters.
d. only pass the gene to his grandsons.
e. pass the gene to all of his children if the mother is a carrier.
Answer: b
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 259
Bloom’s Category: 2. Understanding
71. Alleles for genes located on mitochondrial DNA are said to be maternally inherited.
What is the reason for this pattern of inheritance?
a. The egg and sperm contribute equal numbers of cytoplasmic organelles to the zygote.
b. The egg contributes virtually all of the cytoplasmic organelles to the zygote.
c. Half of the nuclear chromosomes in the zygote come from the father.
d. Half of the nuclear chromosomes in the zygote come from the mother.
e. All of the nuclear chromosomes in the zygote come from the mother.
Answer: b
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259
Bloom’s Category: 2. Understanding
72. Which of the following organelles contain DNA?
a. Nucleus
b. Chloroplast
c. Mitochondria
d. Ribosome
e. a, b, and c
Answer: e
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259
Bloom’s Category: 1. Remembering
73. The approximate total number of genes in the human nuclear genome is closest to
a. 24.
b. 240.
c. 2,400.
d. 24,000.
e. 240,000.
Answer: d
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259
Bloom’s Category: 1. Remembering
74. Humans have _______ genes in their mitochondria.
a. 300
b. 3,000
c. 30,000
d. 300,000
e. 37
Answer: e
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259
Bloom’s Category: 1. Remembering
75. Which of the following is a true statement?
a. The bacterial chromosome is the same size as a eukaryotic chromosome.
b. The bacterial chromosome contains thousands of linked genes.
c. Genetic recombination occurs in bacteria through a conjugation tube.
d. The bacterial chromosome is a highly packed linear strand of DNA.
e. Prokaryotes can exchange genes in a sexual process called epistasis.
Answer: c
Textbook Reference: 12.6 How Do Prokaryotes Transmit Genes?
Page: 260
Bloom’s Category: 2. Understanding
76. What are plasmids?
a. Small circular chromosomes containing a small number of genes.
b. Small segments of genes that replicate independently of the main chromosome of the
cell.
c. Small pieces of DNA used to transfer genes between bacteria
d. Moveable pieces of DNA found in bacteria
e. All of the above
Answer: e
Textbook Reference: 12.6 How Do Prokaryotes Transmit Genes?
Page: 261
Bloom’s Category: 2. Understanding
77. Plasmids are used to
a. break down hydrocarbons.
b. clean up oil spills.
c. produce clones.
d. insert new genetic information into cells.
e. All of the above
Answer: d
Textbook Reference: 12.6 How Do Prokaryotes Transmit Genes?
Page: 261
Bloom’s Category: 2. Understanding
Fill in the Blank
1. A(n) _______ trait is one that can be passed from one generation to another.
Answer: heritable
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 239
Bloom’s Category: 1. Remembering
2. A(n) _______ is an observable feature, such as flower color; a(n) _______ is a
particular form of a character, such as a white flower.
Answer: character; trait
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 239
Bloom’s Category: 1. Remembering
3. A cross between two parents that differs by a single trait is a(n) _______ cross.
Answer: monohybrid
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 1. Remembering
4. When a cross is made and a trait disappears in the F1 generation, only to reappear in
the F2, the trait is probably _______.
Answer: recessive
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 240
Bloom’s Category: 2. Understanding
5. The totality of all the genes of an organism is known as the organism’s _______.
Answer: genome
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 241
Bloom’s Category: 1. Remembering
6. The physical appearance of a character is the _______, whereas the genetic
constitution is the _______.
Answer: phenotype; genotype
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
7. A(n) _______ is a portion of DNA that resides at a particular locus or site on a
chromosome and encodes a particular function.
Answer: gene
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
8. The region of the chromosome occupied by a gene is called the _______.
Answer: locus
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
Bloom’s Category: 1. Remembering
9. A cross between two heterozygous parents that differs by two independent traits is a(n)
_______ cross.
Answer: dihybrid
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 244
Bloom’s Category: 1. Remembering
10. To determine the overall probability of independent events, one should _______ the
probabilities of the individual events.
Answer: multiply
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 245
Bloom’s Category: 2. Understanding
11. To determine the probability of an event that can occur in two or more different ways,
one should _______ the individual probabilities.
Answer: add
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 2. Understanding
12. Mendel’s laws of inheritance can be applied to human genetics through the study of
_______.
Answer: pedigrees
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 1. Remembering
13. One particular allele of a gene may be defined as _______, or standard, because it is
present in most individuals and gives rise to an expected trait, or phenotype.
Answer: wild type
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 248
Bloom’s Category: 2. Understanding
14. The AB phenotype found in individuals with an IAIB genotype is an example of
_______.
Answer: codominance
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 1. Remembering
15. When the expression of one gene depends on the expression of another gene, the
genes demonstrate _______.
Answer: epistasis
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 1. Remembering
16. The hypothesis that hybrid vigor, or heterosis, results from the superiority of the
heterozygote in comparison to either homozygote is known as _______.
Answer: overdominance
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
Bloom’s Category: 1. Remembering
17. When many genes contribute to the phenotype, variation is said to be continuous, or
_______.
Answer: quantitative
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252
Bloom’s Category: 1. Remembering
18. Quantitative variation is the result of the interaction of _______ and _______.
Answer: genes; environment
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252
Bloom’s Category: 1. Remembering
19. Genes at different loci on the same chromosome can separate and recombine to form
_______.
Answer: recombinant chromosomes
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 254
Bloom’s Category: 1. Remembering
20. Recombination is most likely to occur between two loci that are _______.
Answer: far apart
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 254
Bloom’s Category: 2. Understanding
21. Geneticists make use of _______ frequencies to create genetic maps that show the
arrangement of genes on a chromosome.
Answer: recombinant
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 255
Bloom’s Category: 2. Understanding
22. A female that is heterozygous for a recessive sex-linked trait is called a _______.
Answer: carrier
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 259
Bloom’s Category: 2. Understanding
Diagram
1. Refer to the diagram below showing a pedigree of a sex-linked recessive trait. In
generation II, female number 5 marries a man and has three children. One daughter and
one son do not have the recessive trait; the other son does have the recessive trait. Based
on these results, one can conclude that
a. the mother is heterozygous for the trait.
b. the mother is homozygous for the trait.
c. a mutation has occurred.
d. the father is heterozygous for the trait.
e. the father is homozygous for the trait.
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 258
Bloom’s Category: 3. Applying
STUDY GUIDE QUESTIONS
(By Nancy Guild)
Knowledge and Synthesis
1. Hemophilia is a trait carried by the mother and passed to her sons. The allele for
hemophilia, therefore,
a. is carried on one of the mother’s autosomal chromosomes.
b. is carried on the Y chromosome.
c. can be carried on the X or Y chromosome.
d. is on the X chromosome and can only be inherited by the son if the mother is a carrier
(heterozygous).
e. is carried in the mitochondrial genome because sons inherit this allele from their
mothers.
Answer: d
Feedback: Hemophilia is an X-linked trait and can only be inherited by the son from his
mother’s X chromosome (and not her mitochondrial chromosome). The father contributes
the Y chromosome to his son (not his X chromosome) and thus cannot pass any of his Xlinked alleles to his son.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246–247
2. Originally, genetic inheritance was thought to be a function of the blending of traits
from the two parents. Which exception to Mendel’s rules is an example of blending?
a. X linkage
b. Polygenic inheritance
c. Incomplete dominance
d. Codominance
e. Pleiotropism
Answer: c
Feedback: Incomplete dominance results in the progeny’s expressing an intermediate
form of the two parental alleles. (In a cross between red-flowered plants and whiteflowered plants, the expression of pink-flowered plants would be a “blend” of the
parental traits.) Codominance is not an example of blending because both alleles are fully
expressed in the individual.
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 249
3. True-breeding plants
a. produce the same offspring when crossed for many generations.
b have no mutations.
c. result from a monohybrid cross.
d. result from a dihybrid cross.
e. result from crossing over during prophase I of meiosis.
Answer: a
Feedback: Monohybrid and dihybrid crosses produce heterozygous individuals; truebreeding individuals are always homozygous.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 239
4. What is the probability that a cross between a true-breeding pea plant with spherical
seeds and a true-breeding pea plant with wrinkled seeds will produce F1 progeny with
spherical seeds?
a. 1⁄2
b. 1⁄4
c. 0
d. 1⁄8
e. 1
Answer: e
Feedback: This is an example of a monohybrid cross. All of the F1 progeny would have
spherical seeds. (The F1 generation would all have the genotype Ss, producing the
phenotype of spherical seeds because the spherical allele, S, is dominant to the wrinkled
allele, s.)
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 241
5. What is the pattern of inheritance for a rare recessive allele?
a. Every affected person has an affected parent.
b. Unaffected parents can produce children who are affected.
c. Affected parents do not produce affected children.
d. Unaffected mothers have affected sons and daughters who are carriers.
e. None of the above
Answer: b
Feedback: Rare recessive alleles can be carried by both parents but not expressed in those
parents. If the parents are heterozygous for this allele (Aa), their children will have a onefourth probability of expressing that recessive allele (aa). If both parents are affected
(aa), their children will also be affected (aa).
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246–248
6. What is the pattern of inheritance for a rare dominant allele?
a. Every affected person has an affected parent.
b. Unaffected parents can produce children who are affected.
c. Affected parents do not produce affected children.
d. Unaffected mothers have affected sons and daughters who are carriers.
e. None of the above
Answer: a
Feedback: If an allele is dominant, every affected individual has at least one dominant
allele. An affected individual must have received that allele from one of his or her
parents. Because the allele is dominant, that parent must also be affected.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246–248
7. What is the pattern of inheritance for a sex-linked allele?
a. Every affected person has an affected parent.
b. Unaffected parents can produce children who are affected.
c. Affected parents do not produce affected children.
d. Unaffected mothers have affected sons and daughters who are carriers.
e. None of the above
Answer: d
Feedback: The most common sex-linked alleles are X-linked and are passed from a
mother to her son (because the mother always donates one of her X chromosomes to her
son, and the father always donates the Y chromosome to his son). Daughters can also
receive the X-linked allele from their mothers, but the father donates the other X
chromosome, so daughters can be carriers.
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
8. Penetrance and expressivity are related to
a. the increased expression of a particular trait when a hybrid species is formed.
b. quantitative traits that diminish or intensify a particular phenotype.
c. the influence of environment on the expression of a particular genotype.
d. the expression of one gene masking the effects of another gene.
e. the expression of a dominant phenotype in a heterozygote.
Answer: c
Feedback: Penetrance and expressivity are related to the effects the environment has on a
particular phenotype. Answer a refers to hybrid vigor, answer b refers to quantitative
traits, answer d refers to epistasis, and answer e refers to expression of a dominant allele.
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252
9. Sex determination in humans and Drosophila is similar because
a. females are hemizygous.
b. males have one X chromosome and females have two X chromosomes.
c. all males from both species always have one Y chromosome.
d. secondary sex characteristics are determined by genes on the X chromsome.
e. the ratio of X chromosomes to sets of autosomes determines maleness or femaleness.
Answer: b
Feedback: In these species, females have two X chromosomes and males have one X
chromosome. The alleles for secondary sex characteristics are found on the X
chromosome and the autosomes.
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257–258
10. Linked genes are genes that
a. assort independently.
b. segregate equally in the gametes during meiosis.
c. always contribute the same trait to the zygote.
d. are found on the same chromosome.
e. recombine during mitosis.
Answer: d
Feedback: Linked genes by definition are on the same chro-mosome and thus do not sort
independently, do not contribute the same trait to the zygote, and do not recombine
during mitosis or segregate equally to the gametes during meiosis.
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 253
11. Cytoplasmic inheritance
a. results from polygenic nuclear traits.
b. is determined by nuclear genes.
c. is the result of gametes contributing equal amounts of cytoplasm to the zygote.
d. is determined by genes on DNA molecules in mitochondria and chloroplasts.
e. follows Mendel’s law of segregation.
Answer: d
Feedback: The genes on the mitochondria and chloroplast chromosomes which are
cytoplasmically inherited (unlike nuclear genes) are passed on to all of the progeny from
the gamete that contributes the majority of the cytoplasm.
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259–260
12. Epistasis is
a. the degree to which a particular genotype is expressed in an individual.
b. the proportion of individuals within a group with a particular genotype that show the
expected phenotype.
c. a situation in which a heterozygotic individual expresses an intermediate phenotype of
the parents.
d. a situation in which one gene masks the expression of another gene.
e. a situation in which both alleles are expressed equally.
Answer: d
Feedback: Answer a refers to expressivity, answer b refers to penetrance, answer c refers
to incomplete dominance, and answer e refers to codominance.
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250
13. Quantitative traits are traits
a. that are affected by the environment.
b. that affect the same physical characteristic.
c. in which each allele intensifies or diminishes the phenotype.
d. All of the above
e. None of the above
Answer: d
Feedback: Quantitative traits are traits that are affected by the environment and can either
diminish or intensify one phenotype.
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252
14. A test cross
a. is used to determine if an organism that is displaying a dominant trait is heterozygous
or homozygous for that trait.
b. is used to determine if an organism that is displaying a recessive trait is heterozygous
or homozygous for that trait.
c. causes the loss of hybrid vigor.
d. results in an F2 generation with a phenotypic ratio of 3⁄4 dominant to 1⁄4 recessive.
e. results in the same alleles being transferred from generation to generation.
Answer: a
Feedback: A test cross is used to determine if an organism that is expressing a dominant
trait is homozygous or heterozygous for that trait. A ratio of 3⁄4 dominant to 1⁄4 recessive
in the F2 generation results from a monohybrid cross. True-breeding individuals continue
to express the same alleles generation after generation.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 242
15. An individual has a karyotype that is XX but is phenotypically male. What could
explain this result?
a. The Y chromosome was not visible in the karyotype.
b. Sex determination is determined by the autosomes and not the X chromosomes.
c. A translocation has occurred, placing the SRY gene on one of the X chromosomes.
d. The DAX 1 protein is overproduced.
e. A nondisjunction event has resulted in Kleinfelter syndrome.
Answer: c
Feedback: The SRY (sex-determining region) gene has been moved via a translocation to
the X chromosome, and in the presence of the SRY protein, the XX individual has
developed sperm-producing testes. SRY also inhibits the expression of the DAX 1 gene,
which encodes a male inhibitor. If DAX 1 was overproduced during embryonic
development, a female would be produced. Individuals with Klinefelter syndrome are
XXY.
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
16. A bacterial cell’s genotype can be altered by
a. the introduction of a plasmid that carries some of the bacteria’s genes.
b. mating with a bacterial cell with the same genotype.
c. homologous recombination with human DNA.
d. the forming of a conjugation tube with another bacterial cell.
e. the transferring of genetic material from a different strain of bacteria.
Answer: e
Feedback: A bacterial cell’s genotype changes when new genetic information is
introduced either on a plasmid or by conjugation (which requires a conjugation tube and
the transfer of DNA). If conjugation occurs, those genes need to recombine into the
recipient cell’s chromosome to be maintained. Transferring the same genetic information
on a plasmid or mating with a bacterial cell with the same genotype will not change the
genotype of the recipient bacteria. Human DNA cannot recombine with a bacterial
chromosome unless there are identical (homologous) DNA sequences in both DNA
molecules.
Textbook Reference: 12.6 How Do Prokaryotes Transmit Genes?
Page: 260–261
Application
1. Draw a pedigree for three generations in which the grandfather has red–green color
blindness and his daughter is a carrier. This daughter has four sons. Predict how many of
the sons will be color-blind.
Answer: See Figure 12.24, generations II, III, and IV. One-half of her sons could be
color-blind.
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 246–248, 259
2. Draw a sample pedigree with three generations in which the paternal grandfather has a
rare dominant autosomal trait. What is the probability that one of his children will have
the disease? What is the probability that one of his grandchildren will have the disease?
Answer: See Figure 12.10A. One-half of his children could get the disease; one-fourth of
his grandchildren could get the disease.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246–248
3. Draw a sample pedigree with three generations in which the maternal grandmother and
paternal grandfather are carriers of a rare recessive autosomal trait. What is the
probability that one of their children will be carriers of this trait? What is the probability
that a grandchild will have the disease?
Answer: See Figure 12.10B, generations III, and IV. One-half of the children of these
grandparents could be carriers. One-sixteenth of the children could have the disease.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246–248
4. Cytoplasmic traits in certain species of trees are passed from the male plant to all of its
progeny. Compare this observation to cytoplasmic inheritance in humans.
Answer: In humans, the gamete with the largest cytoplasmic contribution is the egg, so
cytoplasmic inheritance is passed from the female parent to all her children. In certain
tree species, the male gamete contributes the majority of the cytoplasm to the zygote, so
all the mitochondria and chloroplasts in the zygote are inherited from the male parent.
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259–260
5. Suppose you are a genetics counselor who is working with a 21-year-old pregnant
woman who has just discovered that her father has Huntington’s chorea, a rare dominant
autosomal trait. This disease usually develops in middle age, so people carrying this trait
do not find out they have this genetic disorder until midlife. What are the chances that the
child she is carrying will develop the disease? (Assume that her husband’s family has no
history of the disease.) What is the chance that she has Huntington’s chorea?
Answer: There is a 50 percent chance that she will develop Huntington’s chorea. Because
the trait is an autosomal dominant allele, one-half of her father’s gametes will contain the
homologous chromosome carrying that allele and one-half of his gametes will contain the
homologous chromosome that carries the wild-type allele. If she received the
Huntington’s allele, her child has a 50 percent chance of receiving this allele from her.
The product rule is used to predict the probability that her child will inherit the
Huntington’s allele: 1⁄2 (the probability that she has the Huntington’s allele) × 1⁄2 (the
probability her child will inherit this allele from her) = 1⁄4 (the probability her child has
the allele). Her child has a 25 percent chance of carrying the Huntington’s chorea allele
and thus of developing the disease.
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246–248
TEXTBOOK SELF-QUIZ
1. In a simple Mendelian monohybrid cross, true-breeding tall plants are crossed with
short plants, and the F1 plants, which are all tall, are allowed to self-pollinate. What
fraction of the F2 generation are both tall and heterozygous?
a. 1⁄8
b. 1⁄4
c. 1⁄3
d. 2⁄3
e. 1⁄2
Answer: e
2. The phenotype of an individual
a. depends at least in part on the genotype.
b. is either homozygous or heterozygous.
c. determines the genotype.
d. is the genetic constitution of the organism.
e. is either monohybrid or dihybrid.
Answer: a
3. The ABO blood groups in humans are determined by a multiple-allele system in which
IA and IB are codominant and are both dominant to IO. A newborn infant is type A. The
mother is type O. Possible phenotypes of the father are
a. A, B, or AB.
b. A, B, or O.
c. O only.
d. A or AB.
e. A or O.
Answer: d
4. Which statement about an individual that is homozygous for an allele is not true?
a. Each of its cells possesses two copies of that allele.
b. Each of its gametes contains one copy of that allele.
c. It is true-breeding with respect to that allele.
d. Its parents were necessarily homozygous for that allele.
e. It can pass that allele to its offspring.
Answer: d
5. Which statement about a test cross is not true?
a. It tests whether an unknown individual is homozygous or heterozygous.
b. The test individual is crossed with a homozygous recessive individual.
c. If the test individual is heterozygous, the progeny will have a 1:1 ratio.
d. If the test individual is homozygous, the progeny will have a 3:1 ratio.
e. Test cross results are consistent with Mendel’s model of inheritance for unlinked
genes.
Answer: d
6. Linked genes
a. must be immediately adjacent to one another on a chromosome.
b. have alleles that assort independently of one another.
c. never show crossing over.
d. are on the same chromosome.
e. always have multiple alleles.
Answer: d
7. In the F2 generation of a dihybrid cross
a. four phenotypes appear in the ratio 9:3:3:1 if the loci are linked.
b. four phenotypes appear in the ratio 9:3:3:1 if the loci are unlinked.
c. two phenotypes appear in the ratio 3:1 if the loci are unlinked.
d. three phenotypes appear in the ratio 1:2:1 if the loci are unlinked.
e. two phenotypes appear in the ratio 1:1 whether or not the loci are linked.
Answer: b
8. The genetic sex of a human is determined by
a. ploidy, with the male being haploid.
b. the Y chromosome.
c. X and Y chromosomes, the male being XX.
d. the number of X chromosomes, the male being XO.
e. Z and W chromosomes, the male being ZZ.
Answer: b
9. In epistasis
a. nothing changes from generation to generation.
b. one gene alters the effect of another.
c. a portion of a chromosome is deleted.
d. a portion of a chromosome is inverted.
e. the behavior of two genes is entirely independent.
Answer: b
10. In humans, spotted teeth are caused by a dominant sex-linked gene. A man with
spotted teeth whose father had normal teeth marries a woman with normal teeth.
Therefore,
a. all of their daughters will have normal teeth.
b. all of their daughters will have spotted teeth.
c. all of their children will have spotted teeth.
d. half of their sons will have spotted teeth.
e. all of their sons will have spotted teeth.
Answer: b
BIOPORTAL DIAGNOSTIC QUIZ (Personalized Study Plan Quiz)
(By Richard McCarty)
1. What fraction of offspring of the cross AaBb × AaBb is homozygous for all the
dominant alleles, assuming that they are on different chromosomes?
a. 1⁄4
b. 1⁄8
c. 1⁄16
d. 1⁄32
e. 1⁄64
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 3. Applying
2. What fraction of the offspring of the cross shown in Question 1 would show the
dominant phenotypes for both genes?
a. 9⁄16
b. 3⁄16
c. 6⁄16
d. 12⁄16
e. 1⁄3
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 3. Applying
3. The cross shown in Question 1 is an example of a _______ cross and the results of
such crosses led Mendel to propose what we now call _______.
a. selfcross; law of segregation of genes
b. dihybrid cross; law of segregation of genes
c. dihybrid cross; law of independent assortment
d. test cross; law of segregation of genes
e. test cross; law of independent assortment
Answer: c
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 2. Understanding
4. _______ is the term for an allele that has more than one distinguishable phenotypic
effect.
a. Pleiotropy
b. Incomplete dominance
c. Codominance
d. Epistasis
e. Heterosis
Answer: a
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 250
Bloom’s Category: 1. Remembering
5. The fact that a trait like height in humans varies over a wide range of values is due to
a. penetrance.
b. expressivity.
c. multiple alleles and the environmental influences on the expression of these genes.
d. epistasis.
e. discrete and qualitative genomic variation.
Answer: c
Textbook Reference: 12.3 How Do Genes Interact?
Page: 252–253
Bloom’s Category: 1. Remembering
6. Coat color in mice involves the effects of multiple gene interactions. If a mouse has
two recessive alleles (aa) for coat color, it is always albino no matter what the genotype
of other genes involved in coat color. This is an example of
a. pleiotropy.
b. incomplete dominance.
c. codominance.
d. epistasis.
e. heterosis.
Answer: d
Textbook Reference: 12.3 How Do Genes Interact?
Page: 250–251
Bloom’s Category: 2. Understanding
7.Codominance
a. occurs when heterozygotes show a phenotype intermediate between those of the two
homozygotes.
b. involves the expression of both alleles at a locus producing two different phenotypes.
c. is only found in mammalian enzyme production.
d. involves one allele having more than one phenotypic effect.
e. would result in pink flowers from a cross between white and red flowers.
Answer: b
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 249–250
Bloom’s Category: 1. Remembering
8. Incomplete dominance
a. results in a phenotypic ratio of 1:2:1 in a monohybrid cross.
b. is far less common than complete dominance.
c. is the same as codominance.
d. involves the distinct expression of both alleles, as in the ABO blood group system.
e. occurs only in X-linked genes.
Answer: a
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 249
Bloom’s Category: 2. Understanding
9. A dramatic departure from expected phenotypic ratios may be the result of
a. environmental influences.
b. linkage.
c. epistasis.
d. gene interactions.
e. All of the above
Answer: e
Textbook Reference: 12.3 How Do Genes Interact?
Page: 251–252
Bloom’s Category: 2. Understanding
10. In many animals, including humans, sex is determined by a single _______, or by a
pair of them. Both males and females have two copies of each of the rest of the
chromosomes, which are called _______.
a. autosome; sex chromosomes
b. gene; autosomes
c. sex chromosome; autosomes
d. gene; sex chromosomes
e. allele; genes
Answer: c
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 256
Bloom’s Category: 1. Remembering
11. In sex-linked inheritance of a recessive gene, all
a. male offspring of a normal male and a heterozygous female carrier would show the
trait.
b. female offspring would be carriers.
c. male offspring who receive the mutant X chromosome would show the trait.
d. female offspring who receive the mutant X would show the trait.
e. Both b and c
Answer: c
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257–259
Bloom’s Category: 4. Analyzing
12. What is the map distance between two genes with a recombination frequency of 0.08?
a. 8 cM
b. 0.08 cM
c. 80 cM
d. 0.8 cM
e. None of the above
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 256
Bloom’s Category: 1. Remembering
13. Genes located on mitochondrial DNA are usually inherited in what fashion?
a. Randomly
b. From the mother
c. From the father
d. Evenly from both the mother and the father
e. By independent assortment
Answer: b
Textbook Reference: 12.5 What Are the Effects of Genes Outside the Nucleus?
Page: 259
Bloom’s Category: 2. Understanding
14. A woman of blood group A has a child with a man of blood group B. The child’s
blood is type O. What are the genotypes of the parents?
a. Mother: IAIA; father: IBIa
b. Mother: IAiO; father: IBIb
c. Mother: IAiO; father: IBiO
d. Mother: IAiB; father: IBIO
e. It is impossible for these individuals to have a child with type O blood.
Answer: c
Textbook Reference: 12.2 How Do Alleles Interact?
Page: 249
Bloom’s Category: 4. Analyzing
15. Unattached earlobes are a dominant trait. Finn and Maggie both have unattached
earlobes but their daughter, Celia, does not. If Finn and Maggie have a second child, what
is the probability that it will have attached earlobes?
a. 1⁄4
b. 1⁄2
c. 3⁄4
d. 1
e. 1⁄8
Answer: a
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 246
Bloom’s Category: 4. Analyzing
16. Wild type fruit flies have red eyes. A white-eyed female fly is crossed with a red-eyed
male fly. All of the females from the cross are red-eyed and all of the males, white-eyed.
What type of inheritance pattern is this?
a. Independent assortment
b. Autosomal dominant
c. Autosomal recessive
d. Incomplete dominance
e. Sex-linked on X chromosome
Answer: e
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 257
Bloom’s Category: 4. Analyzing
17. Sex determination in birds and mammals is similar except that in birds, females are
_______ while in mammals, females are _______.
a. heterogametic; homogametic
b. homogametic; heterogametic
c. haploid; heterogametic
d. diploid; heterogametic
e. None of the above
Answer: a
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 256–257
Bloom’s Category: 2. Understanding
18. The 9:3:3:1 ratio is obtained
a. through a dihybrid cross in which the genes are linked on the same chromosome.
b. through a dihybrid cross in which the genes are on different chromosomes.
c. when crossing over occurs.
d. in a test cross.
e. None of the above
Answer: b
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 244
Bloom’s Category: 2. Understanding
19. Consider a, b, and c, different genes that all reside on the same chromosome. Genes a
and b are 10 cM apart, b and c are 2 cM apart, and a and c are 8 cM apart. What is the
order of these genes?
a. a, b, c
b. a, c, b
c. b, a, c
d. c, a, b
e. The order cannot be determined from the information given.
Answer: b
Textbook Reference: 12.4 What Is the Relationship between Genes and Chromosomes?
Page: 256
Bloom’s Category: 4. Analyzing
20. In a test cross, peas of an unknown genotype are crossed with peas of a known
genotype. In this example, smooth peas are the unknown and wrinkled peas are the
known (rr). If half of the offspring from that cross are smooth and half are wrinkled, what
is the genotype of the unknown plant?
a. Incomplete dominance
b. Homozygous dominant: RR
c. Homozygous recessive: rr
d. Heterozygous: Rr
e. The genotype cannot be determined from the information given.
Answer: d
Textbook Reference: 12.1 What Are the Mendelian Laws of Inheritance?
Page: 241–242
Bloom’s Category: 2. Understanding