ANSC 221 EXAM 3 QUESTIONS AND ANSWERS
An individual that has the same allele of a gene on both chromosomes is said to be: -
Answers -homozygous
If the SsWw individual is mated with another SsWw individual, what is the probability of
producing a SSWW offspring? - Answers -1/16
A geneticist finds that a gene that gives werewolves long fangs also makes them extra
hairy. This is an example of: - Answers -pleiotropy
A situation where alleles at one gene influence the phenotypic expression of alleles of
another gene would be called: - Answers -epistasis
Selected genotypes at the BRCA1 locus in humans have been shown to cause breast
cancer in women. However, not all women with predisposing genotypes will get breast
cancer. This is an example of - Answers -penetrance
Based on Mendel's experimental crosses, what is the expected F2 phenotypic ratio of a
cross between two individuals who are both heterozygous for two independently
assorting genes? - Answers -9:3:3:1
Given the corn plant with the genotype AaBb, what is the probability of the first plant
produced through selfing having the genotype AaBB? - Answers -1/8
You capture several interesting insects from a population in your yard. By inbreeding,
you develop true breeding strains that differ only in the shape of their wings - one strain
has round wings while the other strain has oval wings. How might you demonstrate that
Mendel's principles apply to your insects? - Answers -Set up a dihybrid cross and
determine if your F2 results are predicted by a 9:3:3:1 ratio based on the law of
independent assortment
The dominance hierarchy is as follows: C > c chinchilla > c himilayan > c. What is the
predicted phenotype ratio for the offspring of a cross between a chinchilla rabbit
heterozygous for the himalyan allele and a himilayan rabbit heterozygous for the albino
allele? - Answers -1/2 chinchilla, 1/2 himalayan
In a family with four offspring and both parents heterozygous, what is the probability of
finding the oldest offspring white, while all the others black? (B_ is dominant and bb is
recessive) - Answers -27/256
In the family with four offspring and both parents heterozygous, what is the probability of
finding one white and three black offspring? - Answers -42.2%
Billy Bob: A
, Betty Lou: B
Baby: A
These results show: - Answers -Billy Bob may or may not be the father, more testing is
needed
A pair of co-dominant sex linked alleles in mammals produces red pigment when
homozygous or hemizygous for A1, white when homozygous or hemizygous for A2, and
pink when heterzygous. If a pink female is mated to a white male, we expect progeny: -
Answers -50% of all females are white
During a ________ cross, an individual with the dominant phenotype and unknown
genotype is crossed with a ________ individual to determine the unknown genotype. -
Answers -test; homozygous recessive
Could a recessive mutation in humans be located on the X chromosome if a woman
exhibiting the trait marries a normal man and has a normal son? - Answers -Probably
not
A homozygous 4 o'clock plant with red flowers is crossed to a homozygous 4 o'clock
plant with white flowers. The F1 hybrid is pink flowered and the F2 plants segregate 1
red to 2 pink and to 1 white. This is an example of: - Answers -incomplete dominance
Two mothers give birth to sons at the same time at a busy hospital. The son of couple 1
is diagnosed as having hemophilia, a disease caused by an X-linked recessive allele.
However, neither of the parents is affected. Couple 2 has a normal son despite the fact
that the father has hemophilia. Several years later, couple 1 decides to sue the hospital
claiming that the newborns where switched at birth. Once again, you are asked to be a
genetic consultant. What information can you share with the jury in regards to the
allegations of couple 1 - Answers -a. Because hemophilia is X-linked recessive, the
mother in couple 1 could be heterozygous even though she is normal
c. The x chromosome in male offspring is inherited from the mother, therefore even if
the father has hemophilia he would not pass it to his son.
(Both a and c)
In cattle, SS males and females both have a phenotype called scurred (small
unattached horns). Ss males exhibit the scurred phenotype, whereas Ss females are
not scurred, this is an example of what kind of trait? - Answers -sex-influenced
Dark green skin in frogs is conferred by a dominant allele, G. Light green skin is
determined by a recessive allele,g. Two dark green frogs were mated and 3/4 of the
progeny were dark green and the other 1/4 were light green. What were the genotypes
of the parents? - Answers -Gg and Gg
An individual that has the same allele of a gene on both chromosomes is said to be: -
Answers -homozygous
If the SsWw individual is mated with another SsWw individual, what is the probability of
producing a SSWW offspring? - Answers -1/16
A geneticist finds that a gene that gives werewolves long fangs also makes them extra
hairy. This is an example of: - Answers -pleiotropy
A situation where alleles at one gene influence the phenotypic expression of alleles of
another gene would be called: - Answers -epistasis
Selected genotypes at the BRCA1 locus in humans have been shown to cause breast
cancer in women. However, not all women with predisposing genotypes will get breast
cancer. This is an example of - Answers -penetrance
Based on Mendel's experimental crosses, what is the expected F2 phenotypic ratio of a
cross between two individuals who are both heterozygous for two independently
assorting genes? - Answers -9:3:3:1
Given the corn plant with the genotype AaBb, what is the probability of the first plant
produced through selfing having the genotype AaBB? - Answers -1/8
You capture several interesting insects from a population in your yard. By inbreeding,
you develop true breeding strains that differ only in the shape of their wings - one strain
has round wings while the other strain has oval wings. How might you demonstrate that
Mendel's principles apply to your insects? - Answers -Set up a dihybrid cross and
determine if your F2 results are predicted by a 9:3:3:1 ratio based on the law of
independent assortment
The dominance hierarchy is as follows: C > c chinchilla > c himilayan > c. What is the
predicted phenotype ratio for the offspring of a cross between a chinchilla rabbit
heterozygous for the himalyan allele and a himilayan rabbit heterozygous for the albino
allele? - Answers -1/2 chinchilla, 1/2 himalayan
In a family with four offspring and both parents heterozygous, what is the probability of
finding the oldest offspring white, while all the others black? (B_ is dominant and bb is
recessive) - Answers -27/256
In the family with four offspring and both parents heterozygous, what is the probability of
finding one white and three black offspring? - Answers -42.2%
Billy Bob: A
, Betty Lou: B
Baby: A
These results show: - Answers -Billy Bob may or may not be the father, more testing is
needed
A pair of co-dominant sex linked alleles in mammals produces red pigment when
homozygous or hemizygous for A1, white when homozygous or hemizygous for A2, and
pink when heterzygous. If a pink female is mated to a white male, we expect progeny: -
Answers -50% of all females are white
During a ________ cross, an individual with the dominant phenotype and unknown
genotype is crossed with a ________ individual to determine the unknown genotype. -
Answers -test; homozygous recessive
Could a recessive mutation in humans be located on the X chromosome if a woman
exhibiting the trait marries a normal man and has a normal son? - Answers -Probably
not
A homozygous 4 o'clock plant with red flowers is crossed to a homozygous 4 o'clock
plant with white flowers. The F1 hybrid is pink flowered and the F2 plants segregate 1
red to 2 pink and to 1 white. This is an example of: - Answers -incomplete dominance
Two mothers give birth to sons at the same time at a busy hospital. The son of couple 1
is diagnosed as having hemophilia, a disease caused by an X-linked recessive allele.
However, neither of the parents is affected. Couple 2 has a normal son despite the fact
that the father has hemophilia. Several years later, couple 1 decides to sue the hospital
claiming that the newborns where switched at birth. Once again, you are asked to be a
genetic consultant. What information can you share with the jury in regards to the
allegations of couple 1 - Answers -a. Because hemophilia is X-linked recessive, the
mother in couple 1 could be heterozygous even though she is normal
c. The x chromosome in male offspring is inherited from the mother, therefore even if
the father has hemophilia he would not pass it to his son.
(Both a and c)
In cattle, SS males and females both have a phenotype called scurred (small
unattached horns). Ss males exhibit the scurred phenotype, whereas Ss females are
not scurred, this is an example of what kind of trait? - Answers -sex-influenced
Dark green skin in frogs is conferred by a dominant allele, G. Light green skin is
determined by a recessive allele,g. Two dark green frogs were mated and 3/4 of the
progeny were dark green and the other 1/4 were light green. What were the genotypes
of the parents? - Answers -Gg and Gg
