Download Genetics Spring 2008 Exam 1 Wolf Notes: Below are the correct

2008 Exam 1 key
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Genetics Spring 2008 Exam 1 Wolf
Notes: Below are the correct answers. It may be possible for alternative answers to be correct so if you can convince
me of an alternative answer you will get the points. I will be away until Monday afternoon, so if there is a problem that
needs attention before then, please email Jeremy.
Answers in BOLD
1. Suppose that in plants, smooth seeds (S) are dominant to wrinkled seeds (s) and tall plants (T) are dominant to short
plants (t). You cross a true breeding smooth seeded tall plant with a true breeding wrinkled seeded short plant, you then
backcross the F1 to the parent that was short and wrinkled. What proportion of the progeny is expected to be
heterozygous for tall and smooth?
A. 1/2
B. 1/4
C. 1/8
D. 1/16
E. 0
2. Sickle cell anemia is a recessive trait in humans. In a cross between a father who has sickle cell anemia and a
mother who is heterozygous for the gene, what is the probability that their first three children will be normal?
A. 1/4
B. 1/2
C. none
D. 1/8
E. 1/16 will be albino
3. The following is a list of mitotic events in random order.
A-Chromosomes align on the midplate of the cell.
B-Kinetochores begin attaching to spindle fibers.
C-Nuclear membrane reforms, chromosomes decondense.
D-Chromosomes condense, centrosomes migrate to opposite sides of nucleus.
E-Sister chromatids separate, move to opposite poles.
What is the correct order of events?
A. BDACE
B. DABEC
C. DBAEC
D. ABDCE
E. EDBAC
4. The stage of mitosis when chromosomes condense to form rod-shaped structures visible under the microscope is
called
A. interphase.
B. prophase .
C. metaphase.
D. anaphase.
E. telophase.
5. An allele that expresses its phenotype even when heterozygous with a recessive allele is termed
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A. recessive.
B. recombinant.
C. dominant .
D. parental.
E. independent.
6. An alternative form of a single gene is known as a(n)
A. parental.
B. dihybrid.
C. reciprocal.
D. allele.
E. recessive.
7. A phenotype reflecting a new combination of genes occurring during gamete formation is called
A. a recombinant type.
B. an independent assortment.
C. heterozygous.
D. homozygous.
E. a multihybrid cross.
8. If the parents of a family already have two boys, what is the probability that the next two offspring will be girls?
A. 1
B. 1/2
C. 1/3
D. 1/4
E. 1/8
9. In the following pedigree, the indicated trait is most likely caused by what type of allele?
Square = male, Circle = female
A. autosomal recessive
B. autosomal dominant
C. X-linked recessive
D. X-linked dominant
E. Y-linked
10. The blood groups A, B and O show
A. complete dominance.
B. recessiveness.
C. codominance.
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D. complete dominance, recessiveness, and codominance
E. none of the choices are correct.
11. The stage of mitosis when sister chromatids separate from each other and migrate to opposite poles of a cell is
called
A. interphase.
B. prophase.
C. metaphase.
D. anaphase.
E. telophase.
12. Drosophila melanogaster has four pairs of chromosomes. Sperm from this species are formed by a meiotic process
in which homologous chromosomes pair and segregate but do not undergo crossing over. How many genetically
different kinds of sperm could be produced by a Drosophila melanogaster male?
A. 4
B. 8
C. 16
D. 64
E. 256
13. Crossing over between homologous chromosomes occurs at which of the following stages of meiosis?
A. S phase
B. prophase I
C. metaphase I
D. anaphase I
E. prophase II
14. If a geneticist were to closely examine the make-up of a single autosomal chromosome from one of your cells, that
chromosome would be found to be
A. derived entirely from genes from just one of your grandparents.
B. a mosaic of genes derived from your mother and father.
C. a mosaic of genes derived from all four of your grandparents.
D. a mosaic of genes derived from just two of your grandparents — either your two grandfathers or your two
grandmothers.
E. a mosaic of genes derived from just two of your grandparents — either your maternal grandparents or your
paternal grandparents.
15. Which aspect(s) of chromosome behavior is/are primarily responsible for the tremendous amount of genetic
variability associated with sexual reproduction?
A. Segregation of sister chromatids at anaphase II of meiosis.
B. Segregation of homologous chromosomes at anaphase I of meiosis.
C. Crossing over between homologous chromosomes during prophase I of meiosis.
D. Independent alignment of different homologous pairs on the metaphase I spindle.
E. Both crossing over between homologous chromosomes during prophase I of meiosis and independent
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alignment of different homologous pairs on the metaphase I spindle contribute to the generation of variability.
16. The chromosomal structure to which spindle fibers attach during the mitotic divisions is referred to as a
A. chromatid.
B. centrosome.
C. kinetochore.
D. metaphase plate.
E. centromere.
17. If an individual has 10 gene pairs, how many different gametes can be formed if three of the gene pairs are
homozygous and the remaining 7 gene pairs are heterozygous?
A. 49
B. 100
C. 128
D. 1024
E. 131,072
18. In chickens, it is the females that have two different sex chromosomes (Z and W) while the males have two Z
chromosomes. A Z-linked gene controls the pattern of the feathers with the dominant B allele causing the barred
pattern and the b allele causing non-barred feathers. From which of the following crosses would all of the daughters be
of one type (barred or non-barred) and all of the sons the other type?
A. barred females ´ non-barred males
B. non-barred females ´ barred males
C. non-barred females ´ non-barred males
D. barred females ´ barred males
E. More than one of the choices are correct.
19. Humans have 46 chromosomes. At the end of meiosis 2, each cell contains ______ chromosomes and _______
chromatids.
a. 23 , 46
b. 46 , 46
c. 46 , 92
d. 23 , 23
e. 46 , 23
20. In a traditional statistical analysis (such as the Chi square test), the p-value is the probability of:
A. getting up to the observed deviation from the expected given a FALSE null hypothesis
B. getting up to the observed deviation from the expected given a TRUE null hypothesis
C. the ratios observed being evidence of linkage
D. the ratios observed being evidence of the null hypothesis
E. recombination occurring in the gametes
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21. A true breeding purple flowered plant is crossed with a true breeding pink flowered plant. The F1 have only red
flowers. Intercrossing the F1 produces an F2 in a ratio of 9 red : 3 purple : 3 pink : 1 white.
A. 1 gene with 4 alleles
B. 2 genes, each with 2 alleles related by complete dominance
C. 2 genes, each with 4 alleles related by codominance
D. 3 genes, each with 3 alleles related by complete dominance
E. 2 genes, with recessive epistasis
22. Suppose there are 3 alleles for mouse coat color. AA homozygotes are white, BB homozygotes are brown and CC
homozygotes are black. What is the dominances series of the 3 alleles given the following crosses?
AA BB CC
AAwhitebrownblack
brownbrown
BB
CC
black
• A>B>C
• A>C>B
• B>A>C
• B>C>A
• C>B>A
23. In the following pedigree, the indicated trait is most likely caused by what type of allele?
A. autosomal recessive
B. autosomal dominant
C. X-linked recessive
D. X-linked dominant
E. Y-linked
24. In animal gametogenesis, a single primary spermatocyte generates ______ sperm, while a single primary oocyte
generates ______ egg(s).
A. 1, 4
B. 1, 1
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C. 4, 2
D. 4, 1
E. 4, 4
25. This question can be answered in many ways, including graphics.
1. Define or explain the following 4 terms, as they are used in genetics: dominant, recessive, co-dominant, and
partially (incompletely) dominant. Give examples of each (invent your own if you cannot remember specific ones from
the book).
Dominant: An allele is dominant, relative to a second allele, if it expresses its phenotype in an individual heterozygous
for the two alleles.
Recessive: A recessive allele does not express its phenotype when heterozygous.
Co-dominant: Two alleles are codominant if BOTH are expressed in a heterozygote.
Partially dominant: An allele is partially dominant if the phenotype of the heterozygote is not the same as either
homozygote.
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