9. 6 pts) Labrador retriever dogs come in three flavors yellow, black, and choco
ID: 314775 • Letter: 9
Question
9. 6 pts) Labrador retriever dogs come in three flavors yellow, black, and chocolate. The gene E is needed for coat color deposition and any dog with the genotype e/e will be yellow. If dogs have at least one E allele, they can become brown or black. B encodes for black coloration and the recessive allele b encodes for brown coloration. A dog breeder crosses a true breeding chocolate lab with a true breeding yellow lab to produce all black lab puppies. What were the genotypes of the parents? Yellow Parent: Chocolate Parent:Explanation / Answer
Firstly,according to the information, the true breeding chocolate and yellow parents yielded all offsprings to be black. This means that all the offsprings must have atleast one E allele i.e. they can be either heterozygous or homozygous for allele E at one location.
Secondarily, it can be seen that all the offsprings are specifically black in color. This suggests that all the offsprings must carry atleast one B allele. However, since the information also says that the parents were true breeding chocolate and yellow in color, this means that the offsprings must be heterozygous for both the allele positions. This gives the genotype of the offsprings as EeBb.
This can be possible only if two true breeding parents homozygous at both or atleast one location of genes cross.
This gives the genotypes of parents as:
True breeding chocolate lab parent : EEBb (the parent would be chocolate colored because both the alleles, i.e. for black and brown color are present)
True breeding yellow lab parent : eeBb (the parent would be yellow because E is absent which will help in deposition of color)
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