Bio 340 Exam 2 Questions with Verified Correct
Answers
1:2:0
In a mating between two individuals that are heterozygous for a recessive lethal allele that is
expressed in utero, what genotypic ratio (homozygous dominant:heterozygous:homozygous
recessive) would you expect to observe in the offspring?
BbDd x bbDd
In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced
if the genotype is bb. At an independent locus, gene D produces yellow pigment if the genotype
is D-, but no pigment is produced when the genotype is dd. Production of both pigments results
in brown coat color. If neither pigment is produced, coat color is cream. The genotype of parents
of litters with the following phenotype distribution 3 brown, 3 yellow, 1 black, 1 cream is:
Brown and yellow.
In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced
if the genotype is bb. At an independent locus, gene D produces yellow pigment if the genotype
is D-, but no pigment is produced when the genotype is dd. Production of both pigments results
in brown coat color. If neither pigment is produced, coat color is cream. The phenotype of
parents of litters with the following phenotype distribution 3 brown, 3 yellow, 1 black, 1 cream
is:
Recessive epistasis.
, The wild-type coat color, agouti (AA) is dominant to solid-colored fur (aa). However, a separate
gene C, when present as the recessive homozygote (cc), negates any expression of pigment from
the A gene and results in an albino mouse. Therefore, the genotypes AAcc, Aacc, and aacc all
produce the same albino phenotype. A cross between heterozygotes for both genes (AaCc x
AaCc) would generate offspring with a phenotypic ratio of 9 agouti:3 black:4 albino. Which type
of gene interaction is this?
3/16
Wild type blue-eyed Mary has blue flowers. Two genes control the pathway that makes the blue
pigment: The product of gene W turns a white precursor into magenta pigment. The product of
gene M turns the magenta pigment into blue pigment. Each gene has a recessive loss-of-function
allele: w and m, respectively. A dihybrid (WwMm) is self-pollinated. What proportion of the
offspring will be magenta?
50%
When genes are on different chromosomes, what percentage of gametes produced by a double
heterozygous individual will be recombinant?
50%
A species has n=4 chromosomes. Genes on the same chromosome have a maximum
recombination recombination rate of:
0%
A species has n=4 chromosomes. Genes on the same chromosome have a minimum
recombination recombination rate of:
Answers
1:2:0
In a mating between two individuals that are heterozygous for a recessive lethal allele that is
expressed in utero, what genotypic ratio (homozygous dominant:heterozygous:homozygous
recessive) would you expect to observe in the offspring?
BbDd x bbDd
In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced
if the genotype is bb. At an independent locus, gene D produces yellow pigment if the genotype
is D-, but no pigment is produced when the genotype is dd. Production of both pigments results
in brown coat color. If neither pigment is produced, coat color is cream. The genotype of parents
of litters with the following phenotype distribution 3 brown, 3 yellow, 1 black, 1 cream is:
Brown and yellow.
In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced
if the genotype is bb. At an independent locus, gene D produces yellow pigment if the genotype
is D-, but no pigment is produced when the genotype is dd. Production of both pigments results
in brown coat color. If neither pigment is produced, coat color is cream. The phenotype of
parents of litters with the following phenotype distribution 3 brown, 3 yellow, 1 black, 1 cream
is:
Recessive epistasis.
, The wild-type coat color, agouti (AA) is dominant to solid-colored fur (aa). However, a separate
gene C, when present as the recessive homozygote (cc), negates any expression of pigment from
the A gene and results in an albino mouse. Therefore, the genotypes AAcc, Aacc, and aacc all
produce the same albino phenotype. A cross between heterozygotes for both genes (AaCc x
AaCc) would generate offspring with a phenotypic ratio of 9 agouti:3 black:4 albino. Which type
of gene interaction is this?
3/16
Wild type blue-eyed Mary has blue flowers. Two genes control the pathway that makes the blue
pigment: The product of gene W turns a white precursor into magenta pigment. The product of
gene M turns the magenta pigment into blue pigment. Each gene has a recessive loss-of-function
allele: w and m, respectively. A dihybrid (WwMm) is self-pollinated. What proportion of the
offspring will be magenta?
50%
When genes are on different chromosomes, what percentage of gametes produced by a double
heterozygous individual will be recombinant?
50%
A species has n=4 chromosomes. Genes on the same chromosome have a maximum
recombination recombination rate of:
0%
A species has n=4 chromosomes. Genes on the same chromosome have a minimum
recombination recombination rate of:
