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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Calico cats are female because
A) the Y chromosome has a gene blocking orange coloration.
B) the males die during embryonic development.
C) a male inherits only one of the two X-linked genes controlling hair color.
D) multiple crossovers on the Y chromosome prevent orange pigment production.
E) only females can have Barr bodies.
1)
Refer to the following information to answer the questions below.
A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father
was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant,
and red-green color blindness is X-linked recessive.
2) How many of their daughters might be expected to be color-blind dwarfs?
A) Half
B) None
C) Three out of four
D) One out of four
E) All
2)
3) Which of the following statements is true?
A) Linked genes are found on different chromosomes.
B) The closer two genes are on a chromosome, the lower the probability that a crossover will
occur between them.
C) All of the traits that Mendel studied seed color, pod shape, flower color, and others are due
to genes linked on the same chromosome.
D) Crossing over occurs during prophase II of meiosis.
E) The observed frequency of recombination of two genes that are far apart from each other has
a maximum value of 100%.
3)
4) The following is a map of four genes on a chromosome:
4)
Figure 15.1
Between which two genes would you expect the highest frequency of recombination?
A) A and E
B) E and G
C) W and E
D) A and W
E) A and G
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D, F, and J are three genes in Drosophila. The recombination frequencies for two of the three genes are shown in Figure 15.3.
Figure 15.3
5) Genes D and F could be
A) located on different chromosomes.
B) located very near to each other on the same chromosome.
C) located far from each other on the same chromosome.
D) Both A and B
E) Both A and C
5)
6) If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the
completion of meiosis?
A) Two of the four gametes will be haploid, and two will be diploid.
B) There will be three extra gametes.
C) Half of the gametes will be n + 1, and half will be n — 1.
D) All the gametes will be diploid.
E) 1/4 of the gametes will be n + 1, one will be n — 1, and two will be n.
6)
7) In humans, male-pattern baldness is controlled by an autosomal gene that occurs in two allelic
forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In males,
because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both
with genotype HnHb have a son, what is the chance that he will eventually be bald?
A) 75%
B) 0%
C) 25%
D) 50%
E) 33%
7)
8) Abnormal chromosomes are frequent in malignant tumors. Errors such as translocations may place
a gene in close proximity to different control regions. Which of the following might then occur to
make the cancer worse?
A) Expression of inappropriate gene products
B) An increase in non-disjunction
C) A decrease in mitotic frequency
D) Sensitivity of the immune system
E) Death of the cancer cells in the tumor
8)
9) Women with Turner syndrome have a genotype characterized as which of the following?
A) A karyotype of 47, XXX
B) Mental retardation and short arms
C) A deletion of the Y chromosome
D) aabb
E) A karyotype of 45, X
9)
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10) A couple has a child with Down syndrome when the mother is 39 years old at the time of delivery.
Which is the most probable cause?
A) One member of the couple carried a translocation.
B) One member of the couple underwent nondisjunction in gamete production.
C) One member of the couple underwent nondisjunction in somatic cell production.
D) The woman inherited this tendency from her parents.
10)
11) In order for chromosomes to undergo inversion or translocation, which of the following is
required?
A) Immunological insufficiency
B) Advanced maternal age
C) Point mutation
D) Meiosis
E) Chromosome breakage and rejoining
11)
Figure 15.4
12) The pedigree in Figure 15.4 shows the transmission of a trait in a particular family. Based on this
pattern of transmission, the trait is most likely
A) autosomal recessive.
B) autosomal dominant.
C) sex-linked dominant.
D) mitochondrial.
E) sex-linked recessive.
12)
13) Genomic imprinting is generally due to the addition of methyl (-CH3) groups to C nucleotides in
order to silence a given gene. If this depends on the sex of the parent who transmits the gene, which
of the following must be true?
A) Methylation of C is permanent in a gene.
B) Genes required for early development stages must not be imprinted.
C) The imprints are transmitted only to gamete-producing cells.
D) Methylation must be reversible in ovarian and testicular cells.
E) Methylation of this kind must occur more in males than in females.
13)
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14) Mitochondrial DNA is primarily involved in coding for proteins needed for electron transport.
Therefore in which body systems would you expect most mitochondrial gene mutations to be
exhibited?
A) The skin and senses
B) Nervous and muscular systems
C) Excretory and respiratory systems
D) Circulation
E) The immune system and the blood
14)
15) A certain kind of snail can have a right-handed direction of shell coiling (D) or left handed coiling
(d). If direction of coiling is due to a protein deposited by the mother in the egg cytoplasm, then a
Dd egg-producing snail and a dd sperm-producing snail will have offspring of which genotype(s)
and phenotype(s)?
A) All Dd; half right and half left coiling
B) All Dd; all right coiling
C) 1/2 Dd : 1/2 dd; all right coiling
D) 1/2 Dd : 1/2 dd; half right and half left coiling
E) All Dd; all left coiling
15)
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
16) Pseudohypertrophic muscular dystrophy is an inherited disorder that causes gradual deterioration of the
muscles. It is seen almost exclusively in boys born to apparently normal parents and usually results in death in
the early teens. Is this disorder caused by a dominant or a recessive allele? Is its inheritance sex-linked or
autosomal? How do you know? Explain why this disorder is almost never seen in girls.
17) Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with
normal vision whose father was color-blind. What is the probability that they will have a color-blind daughter?
What is the probability that their first son will be color-blind? (Note the different wording in the two questions.)
18) A fruit fly that is true-breeding for gray body, vestigial wings (b+ b+ vg vg) is mated with one that is
true-breeding for black body, normal wings (b b vg+ vg+ ).
A) Draw the chromosomes for each P generation fly, showing the position of each allele.
B) Draw the chromosomes and label the alleles for an F1 fly.
C) Suppose an F1 female is testcrossed. Draw the chromosomes of the resulting offspring in a Punnett square
like the one at the bottom of Fig. 15.10 in your textbook.
D) Knowing that the distance between these two genes is 17 map units, predict the phenotypic ratios of these
offspring.
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
19) Determine the sequence of genes along a chromosome based on the following
recombination frequencies: A—B, 8 map units; A—C, 28 map units; A—D, 25 map units; B
—C, 20 map units; B—D, 33 map units.
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19)
20) A space probe discovers a planet inhabited by creatures that reproduce with the same
hereditary patterns seen in humans. Three phenotypic characters are height (T = tall, t =
dwarf), head appendages (A = antennae, a = no antennae), and nose morphology (S =
upturned snout, s = downturned snout). Since the creatures are not “intelligent,” Earth
scientists are able to do some controlled breeding experiments, using various
heterozygotes in testcrosses. For tall heterozygotes with antennae, the offspring are:
tall-antennae, 46; dwarf-antennae, 7; dwarf-no antennae, 42; tall-no antennae, 5. For
heterozygotes with antennae and an upturned snout, the offspring are: antennae-upturned
snout, 47; antennae-downturned snout, 2; no antennae-downturned snout, 48; no
antennae-upturned snout, 3. Calculate the recombination frequencies for both
experiments.
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20)