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Genetics
1. If red hair, blue eyes, and freckles were consistently inherited together, the best explanation would be
that
(A) these traits are recessive characteristics
(B) both parents have red hair, blue eyes and freckles
(C) the genes for these traits are linked on the same chromosome
(D) gene duplication have occurred
(E) these traits are dominant to others
(1986 #13)
2. A human genetic defect that affects the ability to metabolize a particular amino acid is
(A) phenylketonuria
(B) hemophilia
(C) sickle cell anemia
(D) Down’s syndrome
(E) Turner’s syndrome
(1986 #16)
3. In a certain group of African people, 4 percent are born with sickle cell anemia. What percentage of
the group has the selective advantage of being more resistant to malaria than those individuals who are
homozygous for normal hemoglobin or for sickle cell anemia?
(A) 2%
(B) 4%
(C) 8%
(D) 16%
(E) 32%
(1986 #54)
Questions 4-6 refer to the pedigree below in which females are indicated by circles and males are
indicated by squares.
4. The genotype of the P1 male must be
(A) OO
(B) AO
(C) BO
(D) AB
(E) AA
(1986 #93)
5. The only other possible genotype for children of the F1 AB male would be
(A) OO
(B) BO
(C) AO
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(D) AA
(E) AB
(1986 #94)
6. The most likely genotype of the mate of the F1 AO female is
(A) AB
(B) BB
(C) OO
(D) AA
(E) BO
(1986 #95)
Questions 6-7
(A) 1/16
(B) 1/4
(C) 1/2
(D) 9/16
(E) 1
Galactosemia is a simple, inherited, autosomal recessive trait. A normal couple
has a child affected with galactosemia. For each of the following situations, select
from the list above the appropriate probability.
6. The probability that the next two children will both be affected with galactosemia
(1986 #74)
7. The probability that the father if the galactosemic child is heterozygous for the recessive allele
(1986 #75)
8. A represents the dominant allele and a represents the recessive allele of a pair. If, in 1,000 offspring,
500 are aa and 500 are of some other genotype, which of the following are probably the genotypes of the
two parents?
(A) Aa and Aa
(B) Aa and aa
(C) AA and Aa
(D) AA and aa
(E) aa and aa
(1990 #5)
9. The primary value of a species type of back cross known as a test cross is to
(A) determine whether a trait is really hereditary
(B) permit detection of recessive genes
(C) reveal cases of blending inheritance
(D) reveal remote ancestors
(E) reveal sex-linked inheritance
(1990 #15)
10. The replacement of glutamic acid by valine at a specific position in the beta chains of hemoglobin
leads to sickle cell anemia. This change represents which of the following mutational events?
(A) DNA base-pair substitution
(B) DNA base-pair deletion
(C) DNA base-pair addition
(D) Chromosomal deletion
(E) Frame-shift mutation
(1990 #32)
11. In corn, the trait for tall plants (T) is dominant to the trait for dwarf plants (t) and the trait for colored
kernels (C) is dominant to the trait for white kernels (c). In a particular cross of corn plants, the probability
of an offspring being tall is 1/2 and the probability of a kernel being colored is 3/4. Which of the following
most probably represents the parental genotypes?
(A) TtCc x ttCc
(B) TtCc x TtCc
(C) TtCc x ttcc
(D) TTCc x ttCc
(E) TTCc x TtCC
(1990 #36)
12.
ABCDEF... -> ABDCEF...
A rearrangement in the linear sequence of genes as shown in the diagram above is known as
(A) duplication
(B) deletion
(C) inversion
(D) polyploidy
(E) translocation
(1990 #37)
13. A form of vitamin D-resistant rickets, known as hypophosphatemia, is inherited as an X-linked
dominate trait. If a male with hypophosphatemia marries a normal female, which of the following
predictions concerning their potential progeny would be true?
(A) All of their sons would inherit the disease.
(B) All of their daughters would inherit the disease.
(C) About 50% of their sons would inherit the disease.
(D) About 50% of their daughters would inherit the disease.
(E) None of their daughters would inherit the disease.
(1990 #44)
14. In a population that is in a Hardy-Weinberg equilibrium, the frequency of a recessive allele for a
certain hereditary trait is .20. What percentage of the individuals in the next generation would be
expected to show the dominant trait?
(A) 8%
(B) 16%
(C) 32%
(D) 64%
(E) 96%
(1990 #61)
15. The relative location of four genes on a chromosome can be mapped from the following data on
crossover frequencies.
Genes
Frequency of crossover
B and C
5%
C and A
15%
A and B
30%
C and B
45%
C and D
50%
Which of the following represents the relative positions of these four genes on the chromosomes?
(A) ABCD
(B) ADCB
(C) CABD
(D) CBAD
(E) DBAC
(1990 #71)
16. In fruit flies, vermilion eyes are a sex-linked recessive characteristic. If a vermilion-eyed female is
crossed with a wild-typed male, what proportion of the male offspring should have vermilion eyes?
(A) 0%
(B) 25%
(C) 50%
(D) 75%
(E) 100%
(1990 #72)
Questions 17-18
The illustrations below represent homologous pairs of chromosomes as they might appear in
various stages of mitosis and meiosis (2n = 2).
17. At which stage do the chromosomes have the LEAST amount of DNA per cell?
(1990 #95)
18. Which diagram represents anaphase of meiosis I?
(1990 #96)
Questions 19-22 refer to the following pedigree that illustrates the inheritance of sickle cell anemia.
Shading indicates the presence of sickle cell anemia.
19. The phenotype of individual C is best explained by the fact that this individual received an allele for
sickle cell anemia from
(A) an autosomal chromosome of each parent
(B) the Y chromosome contributed by the father
(C) the X chromosome contributed by the mother
(D) the X chromosome contributed by the father
(E) the Y chromosome contributed by the mother
(1990 #109)
20. What is the probability that the next child of parents A and B would have had sickle cell anemia?
(A) 0%
(B) 25%
(C) 60%
(D) 75%
(E) 100%
(1990 #110)
21. The most reasonable explanation for the fact that the offspring of C and D do not have sickle cell
anemia is that each received a
(A) sickle allele from the mother
(B) normal allele from the father
(C) sickle allele from the parent
(D) normal allele from each parent
(E) pair of normal alleles from the father
(1990 #111)
22. Which of the following statements is correct about the four offspring of C and D?
(A) Only females are carriers of the sickle cell trait.
(B) Only males are carriers of the sickle cell trait.
(C) Only the females are heterozygous for the sickle cell trait.
(D) All are homologous for the sickle cell trait.
(E) All are carriers of the sickle cell trait.
(1990 #112)
23. If 2n=48 for a particular cell, then the chromosome number in each cell after meiosis would be
(A) 96
(B) 48
(C) 24
(D) 12
(E) 6
(1994.#4)
24. Segregation of alleles does NOT occur in which of the following groups of organisms?
(A) Flowering plants
(B) Insects
(C) Flatworms
(D) Bacteria
(E) Ferns
(1994.#14)
25. Which of the following statements concerning a gene is correct?
(A) A gene can code for a specific protein
(B) A gene can exist in alternate forms called introns
(C) A gene undergoes crossing-over during DNA replication
(D) A gene that is very similar in sequence in a human and in a bacterium is probably a recent mutation.
(E) A gene that is expressed in every offspring of every generation is recessive
(1994.#16)
26. In garden peas, a single gene controls stem length. The recessive allele (t) produces short stems
when homozygous. The dominant allele (T) produces long stems. A short stemmed plant is crossed with
a heterozygous long stemmed plant. Which of the following represents the expected phenotypes of the
offspring and the ratio in which they will occur?
(A) 3 long stemmed plants: 1 short stemmed plant
(B) 1 long stemmed plant: 1 short stemmed plant
(C) 1 long stemmed plant: 3 short stemmed plants
(D) long stemmed plants only
(E) short stemmed plants only
(1994.#27)
Questions 27-28. In a certain flock of sheep, 4 percent of the population has black wool and 96 percent
has white wool. Assume that the population is in Hardy-Weinberg equilibrium.
27. If black wool is a recessive trait, what percent of the population is heterozygous for this trait?
(A) 4%
(B) 20%
(C) 32%
(D) 64%
(E) 80%
(1994.#49)
28. What percent of the population is homozygous for white wool?
(A) 20%
(B) 40%
(C) 64%
(D) 80%
(E) 96%
(1994.#50)
Questions 29-31 refer to the following information
Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the
skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition
is lethal) but heterozygotes will develop to be dwarfed.
Matthew has a family history of the condition, although he does not express the trait. Jane is an
achondroplastic dwarf. Matthew and Jane are planning a family of several children and want to know the
chances of producing a child with achondroplastic dwarfism.
29. The genotypes of Matthew and Jane are best represented as
Matthew
Jane
(A) AA
Aa
(B) Aa
aa
(C) aa
aa
(D) aa
Aa
(E) Aa
Aa
(1994.#99)
30. The probability that Matthew and Jane’s first child will be an achondroplastic dwarf is
(A) 0%
(B) 25%
(C) 50%
(D) 75%
(E) 100%
(1994.#100)
31. If three children are born to Matthew and Jane, what are the chances that the first two children will
not express the trait but that the third child will be an achondroplastic dwarf?
(A) 5/8
(B) 4/8
(C) 3/8
(D) 1/8
(E) 1/16
(1994.#101)
Questions 32-34
A male fruit fly (Drosophila melanogaster) with red eyes and long wings was mated with a female
with purple eyes and vestigial wings. All of the offspring in the F1 generation had red eyes and long
wings.
These F1 flies were test crossed with purple - eyed, vestigial - winged flies. Their offspring, the
F2 generation, appeared as indicated below.
F2 Generation
125 red eyes, long wings
124 purple eyes, vestige wings
18 purple eyes, long wings
16 red eyes, vestigial wings
__________________________
283 Total
32. If in the F1 and F2 generations the same characteristics appeared in both males and females, it
would be safe to assume that these traits for eye color and wing length
(A) are sex-linked
(B) vary in dominance according to sex
(C) are sex-influenced characteristics
(D) are autosomal characteristics
(E) follow the Mendelian rule of independent assortment
(1994.#106)
33. In the F2 generation, the results are best explained by the fact that
(A) the test cross with the F1 flies resulted in sterile offspring
(B) these genes for eye color and wing shape do not pass through the F1 generation
(C) these genes for eye color and wing shape are found on the same chromosome
(D) crossing - over decreases variability
(E) the genes are sex-linked
(1994.#107)
34. If a single locus controls wing shape, then the alleles for this gene act as
(A) dominant-recessive alleles
(B) incomplete-dominance
(C) codominant alleles
(D) multiple alleles
(E) variable alleles
(1994.#108)
35. Assume that genes A and B are not linked. If the probability of allele A in a gamete is 1/2 and the
probability of allele B in a gamete is 1/2, then the probability that both A and B are in the same gamete is
(A.) 1/2 x 1/2
(B.) 1/2 + 1/2
(C.) 1/2  1/2
1/ 2
(E.) 1/ 2 1/ 2
(D.)
(1999 #2)
36. A couple has 5 children, all sons. If the woman gives birth to a sixth child, what is the probability that
the sixth child will be a son?
(A.) 5/6
(B.) 1/2
(C.) 1/5
(D.) 1/6
(E.) 1/64
(1999 #3)
37. Which of the following best describes the parents in a test cross?
(A.) One individual has the dominant phenotype
(B.) Both individuals are heterozygous.
(C.) Both individuals have the dominant phenotype.
(D.) Both individuals have the recessive phenotype.
(E.) Both individuals have an unknown phenotype.
(1999 #9)
38. In sheep, eye color is controlled by a single gene with two alleles. When a homozygous brown-eyed
sheep is crossed with a homozygous green-eyed sheep, blue-eyed offspring are produced. If the blueeyed sheep are mated with each other, what percent of their offspring will most likely have brown eyes?
(99)
(A.) 0%
(B.) 25%
(C.) 50%
(D.) 75%
(E.) 100%
(1999 #11)
39. In peas the trait for tall plants is dominant (T) and the trait for short plants is recessive (t). The trait for
yellow seed color is dominant (Y) and the trait for green seed color is recessive (y). A cross between two
plants results in 296 tall yellow plants and 104 tall green plants. Which of the following are most likely to
be the genotypes of the parents?
(A.) TTYY x TTYY
(B.) TTyy x TTYy
(C.) TtYy x TtYy
(D.) TtYy x TTYy
(E.) TtYY x Ttyy
(1999 # 28)
40. In humans, red-green color blindness is a sex-linked recessive trait. If a man and a woman produce a
color-blind son, which of the following must be true?
(A.) The father is color-blind.
(B.) Both parents carry the allele for color blindness.
(C.) Neither parent carries the allele for color blindness.
(D.) The father carries the allele for color blindness.
(E.) The mother carries the allele for color blindness.
(1999 # 43)
41. In a small group of people living in a remote area, there is a high incidence of “blue skin,” a condition
that results from a variation in the structure of hemoglobin. All of the “blue-skinned” residents can trace
their ancestry to one couple, who were among the original settlers of this region. The unusually high
frequency of “blue skin” in the area is an example of
(A.) mutation
(B.) genetic drift
(C.) natural selection
(D.) sexual selection
(E.) heterozygote advantage
(1999 # 44)
42. Which of the following is the most likely explanation for a high rate of crossing-over between two
genes?
(A.) The two genes are far apart on the same chromosome.
(B.) The two genes are both located near the centromere.
(C.) The two genes are sex-linked.
(D.) The two genes code for the same protein.
(E.) The two genes are on different chromosomes
(1999 #51)
43. Which of the following principles is NOT part of Darwin’s theory of evolution by natural selection?
(A.) Evolution is a gradual process that occurs over long periods of time.
(B.) Variation occurs among individuals in a population.
(C.) Mutations are the ultimate source of genetic variation.
(D.) More individuals are born than will survive.
(E.) Individuals that possess the most favorable variations have the best chance of reproducing.
(1999 #53)
44. In the pedigree above, squares represent males and circles represent females. Individuals who
express a particular trait are represented by shaded figures. Which of the following patterns of
inheritance best explains the transmission of the trait? (99)
(A.) Sex-linked dominant
(B.) Sex-linked recessive
(C.) Autosomal recessive
(D.) Autosomal dominant
(E.) Incompletely dominant
(1999 #56)
Questions 45-46 refer to the birth of a child with blood type A to a mother with blood type B
45. The father must have which of the following blood types?
(A) AB only
(B) Either AB or B
(C) Either AB or O
(D) Either AB or A
(E) AB or A or O
(1999 #102)
46. If the father has blood type AB, which of the following statements is correct about the mother?
A) She contributes an IB allele, which is recessive to the father’s IA allele.
(B) She contributes an i allele, which is recessive to the father’s IA allele.
(C) She contributes an IB allele, which is codominant to the father’s IA allele.
(D) She contributes an i allele, which is codominant to the father’s IB allele.
(E) She is homozygous for the IB allele.
(1999 #103)