Uploaded by Jim Stewart

EXAM 1-Fall 2019 Genetics Biol 303

Biol. 303 EXAM I 9/20/19
-----------------------------------------------------------------------------------------------------------------------------------This exam consists of 40 multiple choice questions worth 2.5 points each. On the separate
answer sheet, please fill-in the single best choice for each question. Please bubble-in your name
on the answer sheet, leaving a space between first and last names. DO NOT BUBBLE-IN AN
--------------------------------------------------------------------------------------------------------------------------------------1. Eukaryotic cells differ from prokaryotic cells in that
A. only eukaryotes have true genetic material.
B. prokaryotes have a nucleus whereas eukaryotes have a nucleoid region
C. prokaryotes have a nucleoid region whereas eukaryotes have a nucleus.
D. None of the above.
2. If two chromosomes of a species are the same length, have identical centromere placements, and
contain similar genes, then these chromosomes most likely are
A. homologous.
B. not homologous.
C. metacentric.
D. sex chromosomes.
Use the following information for questions 3 and 4:
A diploid somatic cell from a certain rodent has a total of 44 chromosomes.
3. How many centromeres are in a somatic cell from this rodent in the G0 phase of the cell cycle?
A. 88
B. 44
C. 22
D. 168
4. What is the total number of telomeres in a normal sperm cell from this rodent?
A. 21
B. 22
C. 44
D. 88
5. The phase of the eukaryotic cell cycle that occurs before the phase when chromosomes are
replicated is known as
A. S phase
B. G1 phase
C. G2 phase
D. mitosis
6. During which step of meiosis does recombination occur?
A. None, since meiosis normally produces genetically identical cells.
B. Telophase I
C. Prophase I
D. Prophase II
7. In somatic cells, sister chromatids
A. exist in the G1 stage of the cell cycle.
B. are not usually identical to one another.
C. are produced during S phase.
D. none of the above, because they only exist in germline cells.
8. A bivalent contains
A. a total of four chromatids
B. a total of two chromatids
C. a pair of nonhomologous autosomes
D. none of the above
9. An allele is
A. a type of cell.
B. a dominant trait.
C. a form of a gene.
D. an imaginary concept.
10. What is the probability that in an organism with a haploid number of 7, a sperm cell will be formed
that contains all 7 chromosomes whose centromeres were derived from paternal homologs?
A. (1/2)10
B. (1/2)7
C. (1/7)2
D. zero
11. In each of Mendel's monohybrid crosses of pea plants, the trait that disappeared in the F 1
A. illustrated the principle of independent assortment.
B. disappeared in the F2 generation.
C. appeared in 3/4 of the plants in F2 generation.
D. none of the above.
12. In each one of Mendel's dihybrid crosses,
A. simple dominance and recessiveness was observed.
B. the phenotypes in the F2 generation segregated in a 9:3:3:1 ratio.
C. epistasis was not evident.
D. all of the above.
13. In the cross (AaBb x AaBb), the genotype AAbb should occur at what frequency? (Assume
independent assortment in all questions unless stated otherwise.)
A. 1/4
B. 1/8
C. 1/2
D. 1/16
14. In a cross between two plants of the following genotypes: (AaBb x AaBb), which one of the
following genotypes should occur at the lowest frequency among the offspring?
A. AaBb
15. The figure below shows a chromosomal separation taking place. Little circles represent
centromeres. The letters stand for genes; capital and lowercase stand for different alleles. 2n in this
organism is 4. What process is shown?
A. anaphase of mitosis
B. telophase of meiosis I
C. anaphase of meiosis I
D. anaphase of meiosis II
b C
16. Referring to the cell in question 15 above, how many bivalents should form in a cell from this
organism during prophase I of meiosis?
A. 4
B. 2
C. 8
D. Not enough information
17. A 9:3:3:1 ratio of phenotypes in the F2 generation of a dihybrid cross
A. holds true only for genes on the same chromosome.
B. indicates that the dihybrid cross is basically equivalent to two independent
monohybrid crosses.
C. is indicative of complete linkage.
D. indicates that an epistatic relationship exists between the two genes under
18. Albinism in humans is inherited as a simple autosomal recessive trait. Two normal parents have
five children and one is albino. If the parents have one more child, what is the probability that the
child will have normal pigmentation?
A. 3/4
B. 1/4
C. 1/2
D. (3/4)5
19. A tall, violet plant is crossed with a dwarf, white plant and all of the F1 offspring are tall, violet.
The F1 plants are selfed to produce the F2 generation. What fraction of the F2 generation would you
expect to dwarf, white? (Assume independent assortment.)
A. 1/4
B. 9/16
C. 3/16
D. 1/16
20. With respect to genes A though F, how many genetically distinct gametes can be formed by an
individual of the following genotype: AABBCCDDEEFf?
A. 26 = 64
B. 2
C. 25 = 32
D. 1
21. A male cat has short hair, a stubby tail, and extra toes. A female cat has long hair, a long tail, and
extra toes. The genes and alleles are as follows:
L = short hair; l = long hair
M = stubby tail; m = long tail
P = extra toes; p = normal number of toes
The two cats have kittens. One kitten has long hair, a long tail, and a normal number of toes. What is
the genotype of the father?
B. Ll Mm PP
C. ll mm pp
D. Ll Mm Pp
22. Red-green color blindness is X-linked recessive. A color-blind woman has children with a man
having normal vision. Which statement is correct?
A. All daughters should be colorblind.
B. All sons should be colorblind.
C. The woman’s father had normal vision.
D. None of the above.
23. Consider three independently assorting genes A, B, and C. What is the probability of obtaining
an offspring that is AaBBcc from parents that are AABbCc and AaBbCc?
A. 1/8
B 1/4
C. 1/16
D. 1/32
24. Consider the following pedigree:
The trait depicted in the above pedigree is likely:
A. autosomal recessive
B. sex-linked recessive
C. autosomal dominant
D. sex-linked dominant
25. In the above pedigree, what is the genotype of the individual that the arrow is pointing to? (The
relevant gene has alleles A and a.)
B. Aa
C. aa
D. Can’t tell
26. If a child is blood type A and the mother is blood type B, what blood type could the father not
A. A
B. B
D. Bombay
27. A condition in which one gene influences the expression of a second gene is called
A. codominance.
B. dominance.
C. recessiveness.
D. epistasis.
28. For the pedigree shown below:
which one of the following modes of inheritance can be ruled out?
A. X- linked dominant
B. X- linked recessive
C. Autosomal dominant
D. All of the above are possible.
29. Shown below is a pedigree for the rare autosomal recessive disease called Tay-Sachs:
genotype Tt?
Consider the woman who is pointed out in the pedigree. If the gene responsible for Tay-Sachs
disease can be symbolized by alleles T and t, what is the probability that the woman’s genotype is
A. 1/4
B. 2/3
C. 1/2
D. No chance, because she must be TT
30. Referring again to Tay-Sachs, if two healthy people who are both heterozygous for the disease
allele have a child, what is the probability that the child will have Tay-Sachs?
A. 1/4
B. 2/3
C. 1/2
D. 3/4
31. Consider two genes A an B that assort independently and have an epistatic relationship.
Consider the cross AaBb x AaBb. Which of the following is true?
A. three distinct phenotypes will appear among the offspring.
B. A must be codominant to B
C. 9/16 of the offspring are expected to have the genotype A- B- (the hyphen represents either
the dominant or recessive allele)
D. none of the above
32. Consider a cross between two people with the following genotypes: AaIAIB x AaIAIB
where alleles A and a display simple dominance/recessiveness for pigmentation (pigmentation is
dominant) and IA and IB are blood type alleles. What fraction of the children should be albino (no
pigmentation) with blood type AB?
A. 6/16
B. 3/16
C. 2/16
D. 1/16
33. Consider a gene with alleles "B" and "b". Suppose that the homozygous recessive genotype bb
is lethal during embryonic development. In a cross between two heterozygotes, Bb x Bb, what
percentage of the offspring born should be Bb?
A. 1/2
B. 1/3
C. 1/4
D. 2/3
34. In “sex-influenced inheritance,”
A. a trait can be expressed in one sex only.
B. a given genotype produces a different phenotype in males versus females.
C. a given trait is on the X chromosome.
D. fathers never pass the trait to sons.
35. When two genes fail to assort independently, the term normally applied is
A. Mendelian inheritance.
B. incomplete dominance.
C. linkage.
D. complementation.
36. Which statement is true?
A. two genes on the same chromosome can assort independently from one another.
B. two genes on different chromosomes will assort independently from one another.
C. two genes close to each other on the same chromosome will probably not display
independent assortment.
D. all of the above.
37. In a typical three factor cross between a heterozygous female and a homozygous recessive male,
offspring arising from double-crossover gametes will be
A. the most common offspring
B. the least common offspring
C. females only
D. males only
38. A particular Drosophila female that is wild-type in appearance is heterozygous for the three
recessive mutations blackbody, curved wings, and purple eyes. When this female is testcrossed, the
following offspring result (arranged as four pairs of phenotypes labeled A-D):
purple 108
Total Progeny
What is the double crossover frequency observed in the three factor cross?
A. 1%
B. 20%
C. 8%
D. 2%
Use the following information for questions 39-40:
In Drosophila, B is the allele for wild type body color and b is the allele for black body color. A second
gene controls wing shape. The shape can be either wild type (V) or vestigial (v). A fly whose
genotype is BbVv has wild type body color and wild type wings. A cross is made between BbVv flies
and flies with black body and vestigial wings. The following phenotypes were observed among the
Wild Type
Normal, vestigial
Black, normal
Black, vestigial
# Observed:
39. Which statement is correct?
A. the genes are linked.
B. there’s evidence of epistasis.
C. the genes are on the same chromosome but assort independently.
D. the genes are on two different chromosomes.
40. What is the genetic distance between the two genes?
A. 185 map units
B. 18.5 centiMorgans
C. genetic distance is not applicable because the genes
assort independently.
D. there’s actually not enough information presented to tell.
That’s all!
Answer Key
Q: 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15,16,17,18,19,20
A: C, A, B, C, B, C, C, A, C, B, D, D, D, D, D, B, B, A, D, B
A: D, B, D, C, B, B, D, B, B, A, C, C, D, B, C, D, B, D, A, B