In Labrador retrievers, black coat color is dominant to brown. Assume that B is

Question

In Labrador retrievers, black coat color is dominant to brown. Assume that B is the allele for black and b is the allele for brown.
a) Suppose that a black Lab is mated with a brown one, and the offspring are 4 black puppies and 1 brown. What can you conclude about the genotype of the black parent?
b) If one of the black offspring from (a) is crossed with a brown puppy, what will be the expected proportion of puppies with black fur in the next generation?
c) If one of the black offspring from (a) is crossed with a black puppy that is known to be heterozygous at the coat color loci, what are the expected phenotypic probabilities of the offspring from this cross? In Labrador retrievers, black coat color is dominant to brown. Assume that B is the allele for black and b is the allele for brown.
a) Suppose that a black Lab is mated with a brown one, and the offspring are 4 black puppies and 1 brown. What can you conclude about the genotype of the black parent?
b) If one of the black offspring from (a) is crossed with a brown puppy, what will be the expected proportion of puppies with black fur in the next generation?
c) If one of the black offspring from (a) is crossed with a black puppy that is known to be heterozygous at the coat color loci, what are the expected phenotypic probabilities of the offspring from this cross? In Labrador retrievers, black coat color is dominant to brown. Assume that B is the allele for black and b is the allele for brown.
a) Suppose that a black Lab is mated with a brown one, and the offspring are 4 black puppies and 1 brown. What can you conclude about the genotype of the black parent?
b) If one of the black offspring from (a) is crossed with a brown puppy, what will be the expected proportion of puppies with black fur in the next generation?
c) If one of the black offspring from (a) is crossed with a black puppy that is known to be heterozygous at the coat color loci, what are the expected phenotypic probabilities of the offspring from this cross?

Explanation / Answer

a) As among the offsprings there is a brown puppy who will require one b allele from both the parent, the genotype of the parents will be Black (Bb) X Brown (bb).

Bb

black

Bb

black

bb

brown

bb

brown

b) If one of the black off spring from a) with genotype Aa is crossed with brown puppy (bb), the cross will be similar to a)

the expected portion of puppies with black fur in the next generation will be 50%

c)Black puppy from cross a) X heterozygous black

Aa X Aa

AA

Black

Aa

Black

Aa

Black

aa

brown

Black = 3/4= 0.75

Brown= 1/4= 0.25

b b B

Bb

black

Bb

black

b

bb

brown

bb

brown

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