Genetics exam test queries and
answers graded A+
Describe Mendel's conclusions about how traits are passed from generation to generation -
ANS✅✅Mendel hypothesized that traits in peas are controlled by specific unit factors. He
suggested that unit factors occur in pairs and that unit factors separate from each other during
gamete formation.
2. How is the chromosome theory of inheritance related to Mendel's findings - ANS✅✅The
chromosome theory of inheritance is based on the parallels between Mendel's model of heredity
and the behavior of chromosomes during meiosis.
3. In meiosis, there are two sequential divisions of the parent cell, producing four daughter cells. In
terms of the behavior of the chromosomes, how does meiosis I compare to meiosis II? - ANS✅✅A.
Homologous chromosomes separate in meiosis I; sister chromatids separate in meiosis II.
One character in peas that Mendel studied was yellow versus green seeds. A cross between a
homozygous yellow line (GG) and a homozygous green line (gg) will result in F1 plants that are
heterozygous (Gg) for this trait and produce yellow seeds. Gg x Gg produces F2 seeds. Conditional
probabilities apply when the pool of possible outcomes is reduced in some way by additional
criteria. Use your knowledge of conditional probabilities and the Punnett square to answer this
question.
4. What is the probability that an F2 seed chosen at random from among only the yellow seeds will
have a genotype of Gg? - ANS✅✅2/3
5. You would like to know whether the progeny of a pair of mated fruit flies in a test cross are
distributed among the resulting four phenotypic classes in a 1:1:1:1 ratio. You perform a chi-square
test and obtain a p value of 0.04. Assuming you have done the test correctly, select the best
interpretation of this result. - ANS✅✅B. The differences between the observed and expected
counts are too large to be attributed to chance.
6. In mice, agouti fur is a dominant trait resulting in individual hairs having a light band of pigment
on an otherwise dark hair shaft. A mouse with agouti fur is shown here, along with a mouse with
solid color fur, which is the recessive phenotype (A = agouti; a = solid color). A separate gene, which
is not linked to the agouti gene, can result in either a dominant black pigment or a recessive brown
pigment (B = black; b = brown). A litter of mice from the mating of two agouti black parents includes
offspring with the following fur colors:
• solid color, black
,• solid color, brown (sometimes called chocolate)
• agouti black
• agouti brown (sometimes called cinnamon)
What would be the expected frequency of agouti brown offspring in the litter? - ANS✅✅3/16
7. In the same mouse species as question 9, a third unlinked gene (gene C/c) also has an epistatic
effect on fur color. The presence of the dominant allele C (for color), allows the A/a and B/b genes to
be expressed normally. The presence of two recessive alleles (cc), on the other hand, prevents any
pigment from being formed, resulting in an albino (white) mouse.
The fourth unlinked gene (gene P/p) also affects fur color.
• For mice that are either homozygous dominant (PP) or heterozygous (Pp), the organism's fur color
is dictated by the other three genes (A/a, B/b, and C/c).
• For mice that are homozygous recessive (pp), large patches of the organism's fur are white. This
condition is called piebaldism.
In a cross between two mice that are heterozygous for agouti, black, color, and piebaldism, what is
the probability that offspring will have solid black fur along with large patches of white fur? -
ANS✅✅9/256
8. Which of the following is the most likely example of codominance? - ANS✅✅A pure-breeding
plant with red flowers is crossed to a pure-breeding plant with white flowers. All their progeny have
flowers with some red patches and some white patches.
9. Cationic trypsinogen is an enzyme made in the pancreas that helps to digest food. It is encoded for
by the PRSS1 gene. Individuals with a disorder called hereditary pancreatitis have mutations in the
PRSS1 gene, which result in inflammation of the pancreas, possibly leading to permanent tissue
damage. The disorder is inherited in an autosomal dominant fashion. Studies of large human
populations have determined that the penetrance of a particular PRSS1 mutation, Arg122His, is 86%.
- ANS✅✅C. They have an 86% chance of showing the associated phenotype.
10. Consider the following family history: Bob has a genetic condition that affects his skin. Bob's wife,
Eleanor, has normal skin. No one in Eleanor's family has ever had the skin condition. Bob and Eleanor
have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their
daughters have the same skin condition as Bob. Based on Bob and Eleanor's family history, what
inheritance pattern does the skin condition most likely follow? - ANS✅✅D. X-linked dominant
11. Which of the following correctly indicates the linkage in the trihybrid parent (MmDdPp -
ANS✅✅A. MDP/mdp
, What can you conclude from the actual data about the location of the three genes in relation to one
another - ANS✅✅The B and C loci are linked and locus A assorts independently from both B and C
loci.
How far apart are the linked genes? - ANS✅✅20 map units
Which of the following statements about the T4 lytic life cycle is false? - ANS✅✅. The phage DNA
is injected into the host and integrates into the bacterial chromosome
In your research on amino acid biosynthesis in E. coli, you have identified three new auxotrophic
mutants in a mutagenesis screen. Each mutant can grow on minimal medium only if it is
supplemented with a specific amino acid, as follows: lys2 mutants require lysine, gly3 mutants
require glycine, and phe1 mutants require phenylalanine.
To determine exconjugant genotypes based on medium composition, which one of the following
statement is not correct? - ANS✅✅lys2- bacteria will grow on minimal medium.
How do mammals, including humans, solve the "dosage problem" caused by the presence of an X
and Y chromosome in one sex and two X chromosomes in the other sex? - ANS✅✅In females, one
of the X chromosomes is condensed and largely inactive so that each sex has one active X
chromosome
When the cloned cat Carbon Copy (CC) was born, she had black patches and white patches, but
completely lacked any orange patches. The knowledgeable students of genetics were not surprised
at this outcome. - ANS✅✅The donor nucleus had an orange allele that was inactivated and
remained inactivated in CC. The remaining black allele was the only one that could be expressed
Which of the following syndromes is not paired with its causative chromosomal aberration? -
ANS✅✅. Fragile X syndrome - deletion
The incidence of Down syndrome, also known as trisomy 21, increases with increasing maternal age.
Which of the following errors most likely produces this condition? - ANS✅✅Nondisjunction during
either meiosis I or II in the female gamete
When a variegated female four o'clock plant is crossed with any male plant, progeny plants can have
either green, white, or variegated leaves. Which of the following statements incorrectly explain this
result? - ANS✅✅The female plant is homozygous in some cells and heterozygous in other cells.
answers graded A+
Describe Mendel's conclusions about how traits are passed from generation to generation -
ANS✅✅Mendel hypothesized that traits in peas are controlled by specific unit factors. He
suggested that unit factors occur in pairs and that unit factors separate from each other during
gamete formation.
2. How is the chromosome theory of inheritance related to Mendel's findings - ANS✅✅The
chromosome theory of inheritance is based on the parallels between Mendel's model of heredity
and the behavior of chromosomes during meiosis.
3. In meiosis, there are two sequential divisions of the parent cell, producing four daughter cells. In
terms of the behavior of the chromosomes, how does meiosis I compare to meiosis II? - ANS✅✅A.
Homologous chromosomes separate in meiosis I; sister chromatids separate in meiosis II.
One character in peas that Mendel studied was yellow versus green seeds. A cross between a
homozygous yellow line (GG) and a homozygous green line (gg) will result in F1 plants that are
heterozygous (Gg) for this trait and produce yellow seeds. Gg x Gg produces F2 seeds. Conditional
probabilities apply when the pool of possible outcomes is reduced in some way by additional
criteria. Use your knowledge of conditional probabilities and the Punnett square to answer this
question.
4. What is the probability that an F2 seed chosen at random from among only the yellow seeds will
have a genotype of Gg? - ANS✅✅2/3
5. You would like to know whether the progeny of a pair of mated fruit flies in a test cross are
distributed among the resulting four phenotypic classes in a 1:1:1:1 ratio. You perform a chi-square
test and obtain a p value of 0.04. Assuming you have done the test correctly, select the best
interpretation of this result. - ANS✅✅B. The differences between the observed and expected
counts are too large to be attributed to chance.
6. In mice, agouti fur is a dominant trait resulting in individual hairs having a light band of pigment
on an otherwise dark hair shaft. A mouse with agouti fur is shown here, along with a mouse with
solid color fur, which is the recessive phenotype (A = agouti; a = solid color). A separate gene, which
is not linked to the agouti gene, can result in either a dominant black pigment or a recessive brown
pigment (B = black; b = brown). A litter of mice from the mating of two agouti black parents includes
offspring with the following fur colors:
• solid color, black
,• solid color, brown (sometimes called chocolate)
• agouti black
• agouti brown (sometimes called cinnamon)
What would be the expected frequency of agouti brown offspring in the litter? - ANS✅✅3/16
7. In the same mouse species as question 9, a third unlinked gene (gene C/c) also has an epistatic
effect on fur color. The presence of the dominant allele C (for color), allows the A/a and B/b genes to
be expressed normally. The presence of two recessive alleles (cc), on the other hand, prevents any
pigment from being formed, resulting in an albino (white) mouse.
The fourth unlinked gene (gene P/p) also affects fur color.
• For mice that are either homozygous dominant (PP) or heterozygous (Pp), the organism's fur color
is dictated by the other three genes (A/a, B/b, and C/c).
• For mice that are homozygous recessive (pp), large patches of the organism's fur are white. This
condition is called piebaldism.
In a cross between two mice that are heterozygous for agouti, black, color, and piebaldism, what is
the probability that offspring will have solid black fur along with large patches of white fur? -
ANS✅✅9/256
8. Which of the following is the most likely example of codominance? - ANS✅✅A pure-breeding
plant with red flowers is crossed to a pure-breeding plant with white flowers. All their progeny have
flowers with some red patches and some white patches.
9. Cationic trypsinogen is an enzyme made in the pancreas that helps to digest food. It is encoded for
by the PRSS1 gene. Individuals with a disorder called hereditary pancreatitis have mutations in the
PRSS1 gene, which result in inflammation of the pancreas, possibly leading to permanent tissue
damage. The disorder is inherited in an autosomal dominant fashion. Studies of large human
populations have determined that the penetrance of a particular PRSS1 mutation, Arg122His, is 86%.
- ANS✅✅C. They have an 86% chance of showing the associated phenotype.
10. Consider the following family history: Bob has a genetic condition that affects his skin. Bob's wife,
Eleanor, has normal skin. No one in Eleanor's family has ever had the skin condition. Bob and Eleanor
have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their
daughters have the same skin condition as Bob. Based on Bob and Eleanor's family history, what
inheritance pattern does the skin condition most likely follow? - ANS✅✅D. X-linked dominant
11. Which of the following correctly indicates the linkage in the trihybrid parent (MmDdPp -
ANS✅✅A. MDP/mdp
, What can you conclude from the actual data about the location of the three genes in relation to one
another - ANS✅✅The B and C loci are linked and locus A assorts independently from both B and C
loci.
How far apart are the linked genes? - ANS✅✅20 map units
Which of the following statements about the T4 lytic life cycle is false? - ANS✅✅. The phage DNA
is injected into the host and integrates into the bacterial chromosome
In your research on amino acid biosynthesis in E. coli, you have identified three new auxotrophic
mutants in a mutagenesis screen. Each mutant can grow on minimal medium only if it is
supplemented with a specific amino acid, as follows: lys2 mutants require lysine, gly3 mutants
require glycine, and phe1 mutants require phenylalanine.
To determine exconjugant genotypes based on medium composition, which one of the following
statement is not correct? - ANS✅✅lys2- bacteria will grow on minimal medium.
How do mammals, including humans, solve the "dosage problem" caused by the presence of an X
and Y chromosome in one sex and two X chromosomes in the other sex? - ANS✅✅In females, one
of the X chromosomes is condensed and largely inactive so that each sex has one active X
chromosome
When the cloned cat Carbon Copy (CC) was born, she had black patches and white patches, but
completely lacked any orange patches. The knowledgeable students of genetics were not surprised
at this outcome. - ANS✅✅The donor nucleus had an orange allele that was inactivated and
remained inactivated in CC. The remaining black allele was the only one that could be expressed
Which of the following syndromes is not paired with its causative chromosomal aberration? -
ANS✅✅. Fragile X syndrome - deletion
The incidence of Down syndrome, also known as trisomy 21, increases with increasing maternal age.
Which of the following errors most likely produces this condition? - ANS✅✅Nondisjunction during
either meiosis I or II in the female gamete
When a variegated female four o'clock plant is crossed with any male plant, progeny plants can have
either green, white, or variegated leaves. Which of the following statements incorrectly explain this
result? - ANS✅✅The female plant is homozygous in some cells and heterozygous in other cells.
