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BSC2010 Genetics Questions with Answers
(100% Correct Answers)
Suppose coat color in a rodent is due to a single gene, with the allele for red fur
being dominant to the allele for white fur. In the F2 generation resulting from a
cross between true breeding red rodents and true breeding white rodents,
_______ of the rodents should have red fur. Answer: 75%
A woman has blood type AB. From this, we can infer that Answer: neither of
her parents was type O
One true-breeding line of mice is obese and dark and another is lean and light.
Dark is dominant to light, but obese and lean exhibit incomplete dominance.
What proportion of offspring from a dihybrid cross should be both dark and
intermediate between obese and lean? Answer: 3/8
Consider the progeny of a dihybrid cross. For every double recessive
homozygote observed, you can expect _______ double dominant
homozygote(s). Answer: 1
If the allele for tall (T) plants is incompletely dominant over the allele for short
(t) plants, what offspring would result from crossing two Tt plants? Answer:
1/4 tall, 1/2 intermediate height, 1/4 short
Which cannot be a probability value? Answer: -0.14
In tomatoes, tall is dominant to dwarf, and smooth fruits are dominant to hairy
fruits. A plant homozygous for both dominant traits is crossed with a plant
homozygous for both recessive traits. The F1 progeny are crossed with the
following results: l93 tall with smooth fruits; 87 dwarf with hairy fruits; 11 tall
with hairy fruits; and 9 dwarf with smooth fruits. These data indicate that the
genes are Answer: linked and show 10% recombination
A human female is heterozygous for a recessive X-linked trait. She has children
with a male who does not have the trait. Their sons have a _______ probability
, 2
of expressing the trait, while their daughters have a probability of _______ of
expressing the trait. Answer: 0.5,0
The probability that event A will occur is x (a value between 0 and 1). The
probability that event B will occur is y (a different value between 0 and 1).
Assuming that events A and B are independent of each other, what is the
probability that both events will occur? Answer: X (x) Y
Locus A and locus B recombine with 10 percent frequency. Locus A and locus
C recombine with 23 percent frequency. Locus B and locus D recombine with 4
percent frequency. Locus D and locus E do not recombine. Based on this
information, which pairs of loci are most likely to be closest together? Answer:
D and E
In Drosophila, production of eye color pigment requires a functional protein
encoded by the white locus. Individuals with two copies of the w allele lack any
eye color pigment; individuals with at least one wild-type allele have pigment.
The bw allele at the brown locus produces a defective enzyme responsible for
converting one type of pigment to another. Individuals with two bw alleles
have brown eyes; individuals with at least one wild-type allele at the brown
locus have normal red eyes (assuming that they have eye pigment). Which of
the following is true? Answer: The white locus is epistatic to the brown locus
Due to the phenomenon of dominance, Answer: different genotypes can result
in the same phenotype
In horses, hairs can be black because of allele H1 or white because of allele H2.
Horses with both alleles are called blue roans because they have both white and
black hairs. Thus, Answer: H1 and H2 exhibit codominance
In horses, hairs can be black because of allele H1 or white because of allele H2.
Horses with both alleles are called blue roans because they have both white and
black hairs. What are the expected phenotypic ratios if you crossed blue roan
individuals to black individuals? Answer: Half would be black, half would be
blue roan
BSC2010 Genetics Questions with Answers
(100% Correct Answers)
Suppose coat color in a rodent is due to a single gene, with the allele for red fur
being dominant to the allele for white fur. In the F2 generation resulting from a
cross between true breeding red rodents and true breeding white rodents,
_______ of the rodents should have red fur. Answer: 75%
A woman has blood type AB. From this, we can infer that Answer: neither of
her parents was type O
One true-breeding line of mice is obese and dark and another is lean and light.
Dark is dominant to light, but obese and lean exhibit incomplete dominance.
What proportion of offspring from a dihybrid cross should be both dark and
intermediate between obese and lean? Answer: 3/8
Consider the progeny of a dihybrid cross. For every double recessive
homozygote observed, you can expect _______ double dominant
homozygote(s). Answer: 1
If the allele for tall (T) plants is incompletely dominant over the allele for short
(t) plants, what offspring would result from crossing two Tt plants? Answer:
1/4 tall, 1/2 intermediate height, 1/4 short
Which cannot be a probability value? Answer: -0.14
In tomatoes, tall is dominant to dwarf, and smooth fruits are dominant to hairy
fruits. A plant homozygous for both dominant traits is crossed with a plant
homozygous for both recessive traits. The F1 progeny are crossed with the
following results: l93 tall with smooth fruits; 87 dwarf with hairy fruits; 11 tall
with hairy fruits; and 9 dwarf with smooth fruits. These data indicate that the
genes are Answer: linked and show 10% recombination
A human female is heterozygous for a recessive X-linked trait. She has children
with a male who does not have the trait. Their sons have a _______ probability
, 2
of expressing the trait, while their daughters have a probability of _______ of
expressing the trait. Answer: 0.5,0
The probability that event A will occur is x (a value between 0 and 1). The
probability that event B will occur is y (a different value between 0 and 1).
Assuming that events A and B are independent of each other, what is the
probability that both events will occur? Answer: X (x) Y
Locus A and locus B recombine with 10 percent frequency. Locus A and locus
C recombine with 23 percent frequency. Locus B and locus D recombine with 4
percent frequency. Locus D and locus E do not recombine. Based on this
information, which pairs of loci are most likely to be closest together? Answer:
D and E
In Drosophila, production of eye color pigment requires a functional protein
encoded by the white locus. Individuals with two copies of the w allele lack any
eye color pigment; individuals with at least one wild-type allele have pigment.
The bw allele at the brown locus produces a defective enzyme responsible for
converting one type of pigment to another. Individuals with two bw alleles
have brown eyes; individuals with at least one wild-type allele at the brown
locus have normal red eyes (assuming that they have eye pigment). Which of
the following is true? Answer: The white locus is epistatic to the brown locus
Due to the phenomenon of dominance, Answer: different genotypes can result
in the same phenotype
In horses, hairs can be black because of allele H1 or white because of allele H2.
Horses with both alleles are called blue roans because they have both white and
black hairs. Thus, Answer: H1 and H2 exhibit codominance
In horses, hairs can be black because of allele H1 or white because of allele H2.
Horses with both alleles are called blue roans because they have both white and
black hairs. What are the expected phenotypic ratios if you crossed blue roan
individuals to black individuals? Answer: Half would be black, half would be
blue roan
