Question

UESTION 4 Background info: in Labrador retrievers there is a gene, called black that participates in determining coat colour. This gene has two alleles, B and b. There are two other genes that participate in determining coat colour in Labs: the extension gene (with alleles E and e) and the agouti gene. All Labs are homozygous mutant for the agouti gene (so we can ignore this gene in our analyses and in our predictions, because it is not a variable). Labs with a black coat colour can have genotype B/B; E/E or B/B; E/e or B/b; E/E or B/b; E/e. Labs with a brown coat colour can have genotype b/b; E/e or b/b; E/E. Labs with a yellow coat colour can have genotype B/B; e/e or B/b; e/e or b/b; e/e. At the molecular level, the B allele codes for a version of “protein B” that produces black pigment; the b allele codes for a version of “protein b” that produces brown pigment, the E allele codes for a version of “protein E” that allows the pigment (black or brown) to be deposited in the fur of the dog, and the e allele codes for a version of “protein E” that does not allow the pigment (black or brown) to be deposited in the fur of the dog, resulting in a yellowish colour. What is the dominance relationship between the black and the brown coat colour phenotypes? a.Black is dominant to brown. b.Brown is dominant to black c.Black is neither dominant nor recessive to brown. d.We need additional information to answer the question.

Answer 1

Labs with a black coat colour can have genotype B/B; E/E or B/B; E/e or B/b; E/E or B/b; E/e.

Answer: all are possible

Labs with a brown coat colour can have genotype b/b; E/e or b/b; E/E.

Answer: all are possible

Labs with a yellow coat colour can have genotype B/B; e/e or B/b; e/e or b/b; e/e

Answer: all are possible

Solution in image