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In Labrador retrievers coat color is controlled by two independently assorting loci. The B locus controls...

In Labrador retrievers coat color is controlled by two independently assorting loci. The B locus controls hair color; black (B) is dominant to chocolate (b). A second locus, E, allows for deposition of the color on the hairs. The homozygous recessive condition at this locus (ee) produces a yellow dog, regardless of whether the animal is BB, Bb, or bb. You discover that your female yellow Labrador is pregnant, and she delivers a litter of 5 black puppies, 2 chocolate puppies and 3 yellow puppies.

(a) Is the father of the puppies the yellow Labrador from next door or the black Labrador from down the street? How do you know?

(b) What is the genotype of the father?

(c) What is the genotype of the mother?

(d) What is the genotype of the chocolate puppies?

(e) You also have a chocolate Labrador female that comes from a pedigreed family of entirely chocolate Labradors. You mate her to a yellow Labrador male that came from a family of 14 black Labrador and 5 yellow Labrador brothers and sisters. The pedigree for the family of the male only contains black and yellow Labradors going back several generations. What is/are the expected phenotype(s) and genotype(s) of the offspring of this mating and in what proportions?

Solutions

Expert Solution

Answer: At first we should understand about the genes. Both the genes are independently assorting durnig segregation. But one gene at loci E is regulating the phenotype of Loci B, so this is an epistatic condition.

As the genes are independently assorting so we can make a table of all possible combination of the alleles of these genes.

BE Be bE be
BE

BBEE

(Black)

BBEe

(Black)

BbEE

(Black)

BbEe

(Black)
Be

BBEe

(Black)

BBee

(Yellow)

BbEe

(Black)

Bbee

(Yellow)
bE

BbEE

(Black)

BbEe

(Black)

bbEE

(Choclate)

bbEe

(Choclate)
be

BbEe

(Black)

Bbee

(Yellow)

bbEe

(Choclate)

bbee

(Yellow)

A) By the table we have all the possible genotype for the three different phenotype. As the Female is Yellow so the possible genotype for her loci E can be ; ee. And Possible gametes from her will be ; e . As she has a yellow puppy so one allele mus come from father to make it "ee". Possible genetype of father for Loci E is Ee/ee

Now she delivers baby with colors Black, choclate, yellow. Black is dominant so its single allele is enough. But she also produces Choclate puppy for that the condition should be homozygous (bb). So she must contribute allele b. For Loci B for mother can be : Bb. Same applies to the father. Both mother and father must be having atleast one recessive allele b. Possible genotype at Loci B for father can be "Bb"only.

If it has ee than it has yellow color but if it has Ee it can have either Black or choclate color. As both theYellow and the Black Labrador can contribute allele "e". So both of them can be father.

b) Possible genotype of father Black labrador BbEe and for Yellowlabrador it is Bbee.

c) Possible genotype of mother is Bbee.

d) Choclate Puppies genotype can be bbEe.

gladiator answered 2 years ago
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