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Inspector Exam CA
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Chapter 2
Single-Gene Inheritance
MULTIPLE-CHOICE QUESTIONS
Sections 2.1. and 2.2. (Single gene inheritance, The chromosomal basis of single-gene
inheritance patterns)
1. If a plant of genotype A/a is selfed, and numerous offspring are scored, what proportion of the
progeny is expected to have homozygous genotypes?
A) 0
B) 25%
C) 50%
D) 75%
E) 100%
Answer: C
2. What is the maximum number of heterozygous genotypes that could be produced by
monohybrid self?
A) 1
B) 2
C) 3
D) 4
E) 6
Answer: A
3. A plant is heterozygous at three loci. How many different gamete genotypes can it theoretically
produce with respect to these three loci?
A) 2
B) 3
C) 4
D) 8
E) 16
Answer: D
,4. In mountain rabbits, the EL-1 gene is located on chromosome 3. Four alleles of this gene have
been identified in the population. With respect to EL-1, what is the maximum number of
genotypes in the progeny of a single cross between two mountain rabbits?
A) 1
B) 2
C) 3
D) 4
E) 6
Answer: D
5. A wild-type strain of haploid yeast is crossed to a mutant strain with phenotype d. What
phenotypic ratios will be observed in the progeny?
A) all wild type
B) 75% wild type and 25% mutant (d)
C) 50% wild type and 50% mutant (d)
D) 25% wild type and 75% mutant (d)
E) all mutant (d)
Answer: C
Section 2.3. (The molecular basis of Mendelian inheritance patterns)
6. Mice (Mus musculus) have 40 chromosomes per diploid cell (2n = 40). How many double-
stranded DNA molecules and how many chromosomes are there in a mouse cell that is in the G2
stage of the cell cycle?
A) 40 DNA molecules and 20 chromosomes
B) 40 DNA molecules and 40 chromosomes
C) 40 DNA molecules and 80 chromosomes
D) 80 DNA molecules and 40 chromosomes
E) 80 DNA molecules and 80 chromosomes
Answer: D
7. A mutation occurs in a germ cell of a pure-breeding, wild-type male mouse prior to DNA
replication. The mutation is not corrected, and the cell undergoes DNA replication and a normal
meiosis producing four gametes. How many of these gametes will carry the mutation?
A) 1
B) 2
C) 3
D) 4
E) It is impossible to predict.
Answer: B
, 8. What is the mechanism that ensures Mendel’s first law of segregation?
A) formation of chiasmata
B) formation of the kinetochore
C) pairing of homologous chromosomes
D) segregation of homologous chromosomes during meiosis I
E) segregation of sister chromatids during meiosis II
Answer: D
9. A laboratory mouse homozygous for an RFLP marker is mated to a wild mouse that is
heterozygous for that marker. One of the heterozygous individuals resulting from this cross is
mated back to the wild parent. What proportion of the offspring will have the same RFLP pattern
as the original laboratory mouse?
A) none of the offspring
B) 1/4
C) 1/2
D) 3/4
E) all of the offspring
Answer: C
10. The diagram below shows a part of the biochemical pathway responsible for fruit color in
peppers (Caspicum annuum). Enzyme 1 is responsible for catalyzing the reaction that turns the
colorless precursor into yellow pigment, whereas Enzyme 2 catalyzes the step that turns the
yellow pigment into red pigment. A breeder crosses a pure-breeding plant that makes yellow
peppers to a pure-breeding plant that makes red peppers. What proportion of the offspring will
make red peppers?
Enzyme 1 Enzyme 2
Colorless precursor Yellow pigment Red pigment
A) all of the offspring
B) 3/4
C) 1/2
D) 1/4
E) none of the offspring
Answer: A
11. The wild-type eye color in the fruit fly Drosophila melanogaster is dark red, as a result of a
mixture of bright red and brown pigments. “Enzyme A” is encoded by the “a” gene, and is
required to synthesize the bright red pigment. A lack of red pigment results in a somewhat brown
eye color. You cross two fruit flies who are heterozygous for a recessive mutation that completely
inactivates the “a” gene. What proportion of their offspring will have a recessive eye color
phenotype?
Inspector Exam CA
Save
Start a student pass
Chapter 2
Single-Gene Inheritance
MULTIPLE-CHOICE QUESTIONS
Sections 2.1. and 2.2. (Single gene inheritance, The chromosomal basis of single-gene
inheritance patterns)
1. If a plant of genotype A/a is selfed, and numerous offspring are scored, what proportion of the
progeny is expected to have homozygous genotypes?
A) 0
B) 25%
C) 50%
D) 75%
E) 100%
Answer: C
2. What is the maximum number of heterozygous genotypes that could be produced by
monohybrid self?
A) 1
B) 2
C) 3
D) 4
E) 6
Answer: A
3. A plant is heterozygous at three loci. How many different gamete genotypes can it theoretically
produce with respect to these three loci?
A) 2
B) 3
C) 4
D) 8
E) 16
Answer: D
,4. In mountain rabbits, the EL-1 gene is located on chromosome 3. Four alleles of this gene have
been identified in the population. With respect to EL-1, what is the maximum number of
genotypes in the progeny of a single cross between two mountain rabbits?
A) 1
B) 2
C) 3
D) 4
E) 6
Answer: D
5. A wild-type strain of haploid yeast is crossed to a mutant strain with phenotype d. What
phenotypic ratios will be observed in the progeny?
A) all wild type
B) 75% wild type and 25% mutant (d)
C) 50% wild type and 50% mutant (d)
D) 25% wild type and 75% mutant (d)
E) all mutant (d)
Answer: C
Section 2.3. (The molecular basis of Mendelian inheritance patterns)
6. Mice (Mus musculus) have 40 chromosomes per diploid cell (2n = 40). How many double-
stranded DNA molecules and how many chromosomes are there in a mouse cell that is in the G2
stage of the cell cycle?
A) 40 DNA molecules and 20 chromosomes
B) 40 DNA molecules and 40 chromosomes
C) 40 DNA molecules and 80 chromosomes
D) 80 DNA molecules and 40 chromosomes
E) 80 DNA molecules and 80 chromosomes
Answer: D
7. A mutation occurs in a germ cell of a pure-breeding, wild-type male mouse prior to DNA
replication. The mutation is not corrected, and the cell undergoes DNA replication and a normal
meiosis producing four gametes. How many of these gametes will carry the mutation?
A) 1
B) 2
C) 3
D) 4
E) It is impossible to predict.
Answer: B
, 8. What is the mechanism that ensures Mendel’s first law of segregation?
A) formation of chiasmata
B) formation of the kinetochore
C) pairing of homologous chromosomes
D) segregation of homologous chromosomes during meiosis I
E) segregation of sister chromatids during meiosis II
Answer: D
9. A laboratory mouse homozygous for an RFLP marker is mated to a wild mouse that is
heterozygous for that marker. One of the heterozygous individuals resulting from this cross is
mated back to the wild parent. What proportion of the offspring will have the same RFLP pattern
as the original laboratory mouse?
A) none of the offspring
B) 1/4
C) 1/2
D) 3/4
E) all of the offspring
Answer: C
10. The diagram below shows a part of the biochemical pathway responsible for fruit color in
peppers (Caspicum annuum). Enzyme 1 is responsible for catalyzing the reaction that turns the
colorless precursor into yellow pigment, whereas Enzyme 2 catalyzes the step that turns the
yellow pigment into red pigment. A breeder crosses a pure-breeding plant that makes yellow
peppers to a pure-breeding plant that makes red peppers. What proportion of the offspring will
make red peppers?
Enzyme 1 Enzyme 2
Colorless precursor Yellow pigment Red pigment
A) all of the offspring
B) 3/4
C) 1/2
D) 1/4
E) none of the offspring
Answer: A
11. The wild-type eye color in the fruit fly Drosophila melanogaster is dark red, as a result of a
mixture of bright red and brown pigments. “Enzyme A” is encoded by the “a” gene, and is
required to synthesize the bright red pigment. A lack of red pigment results in a somewhat brown
eye color. You cross two fruit flies who are heterozygous for a recessive mutation that completely
inactivates the “a” gene. What proportion of their offspring will have a recessive eye color
phenotype?
