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Chromosome Variations
*1. Which types of chromosome mutations
a. increase the amount of genetic material on a particular chromosome?
b. increase the amount of genetic material for all chromosomes?
c. decrease the amount of genetic material on a particular chromosome?
d. change the position of genes on a single chromosome without changing the amount of genetic
material?
e. move genes from one chromosome to a nonhomologous chromosome?
*2. A chromosome has the segments labeled below, where • represents the centromere.
A B
•C
D E F G
What types of chromosome mutations are required to alter this chromosome to each of the following chromosomes? (In some cases, more than one chromosome mutation may be required.)
a.
A B A B
b. A B
c.
A B
d. A
e.
A
f.
A
g.
C
h. A
i.
A
•C
•C
•C
D E F G
D E A B F G
F E DG
•CDEFG
B • C D E
B • E D C F G
•BADEFG
B • C F E D F E D G
B • C D E F C D F E
G
*3. A species has 2n = 16. How many chromosomes will be found per cell in each of the following
mutants in this species?
a. Monosomic
b. Autotriploid
Pierce, Genetics: A Conceptual Approach
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Pierce, Genetics: A Conceptual Approach
Chapter 9 Chromosome Variations
c. Autotetraploid
d. Trisomic
e. Double monosomic
f. Nullisomic
g. Autopentaploid
h. Tetrasomic
**4. The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Females heterozygous for Notch have an indentation on the margin of their wings; Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that
contains the locus for white eyes, an X-linked recessive trait. Give the phenotypes and proportions of
progeny produced in the following crosses.
a. A red-eyed, Notch female is mated to a white-eyed male.
b. A white-eyed, Notch female is mated to a red-eyed male.
c. A white-eyed, Notch female is mated to a white-eyed male.
**5. The green nose fly normally has six chromosomes—two metacentric and four acrocentric. A
geneticist examines the chromosomes of an odd-looking green nose fly and discovers that it only has
five chromosomes; three of these are metacentric and two are acrocentric. Explain how this change in
chromosome number might have occurred.
*6. Species I is diploid (2n = 6) with chromosomes AABBCC; related species II is diploid (2n = 6) with
chromosomes MMNNOO. Give the chromosomes that would be found in individuals with the following chromosome mutations.
a. Trisomic for chromosome A
b. Tetrasomic for chromosome N
c. An autotriploid of species I
d. An allotetraploid
e. An autotetraploid of species II
f. Monosomic for chromosome B
g. A double trisomic for chromosomes A and C
h. A nullisomic for chromosome O
**7. Red-green colorblindness is an X-linked recessive disorder in humans. A young man with an XXY
karyotype (Klinefelter syndrome) is colorblind. His XY brother is also colorblind. Both parents have
normal color vision. Where did the nondisjunction occur that gave rise to the young man with
Klinefelter syndrome?
**8. Bill and Betty have had two children with Down syndrome. Bill’s brother has Down syndrome,
and his sister has two children with Down syndrome. Based on these observations, which of the following is most likely correct? Explain your reasoning.
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Pierce, Genetics: A Conceptual Approach
Chapter 9 Chromosome Variations
a. Bill has 47 chromosomes.
b. Betty has 47 chromosomes.
c. Bill and Betty’s children have 47 chromosomes.
d. Bill’s sister has 45 chromosomes.
e. Bill has 46 chromosomes.
f. Betty has 45 chromosomes.
g. Bill’s brother has 45 chromosomes.
**9. In mammals, sex chromosome aneuploids are more common than autosomal aneuploids, but in
fish, sex chromosome aneuploids and autosomal aneuploids occur with equal frequency. Offer an
explanation for these differences between mammals and fish.
***10. A young couple is planning to have children. Knowing that there have been a substantial number of stillbirths, miscarriages, and fertility problems on the husband’s side of the family, they see a
genetic counselor. A chromosome analysis reveals that while the woman has a normal karyotype, the
man possesses only 45 chromosomes and is a carrier for a Robertsonian translocation involving chromosomes 22 and 13.
a. List all the different types of gametes that might be produced by the man.
b. What types of zygotes will develop when each of the gametes produced by the man fuses with a normal
gamete from the woman?
c. If trisomies and monosomies involving chromosome 13 and 22 are lethal, what proportion of the
surviving offspring will be carriers of the translocation?
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