Labrador retrievers have 2 unlinked genes that affect coat color. The \"color\"
ID: 87659 • Letter: L
Question
Labrador retrievers have 2 unlinked genes that affect coat color. The "color" B gene: B is the dominant allele for black hair and b is the recessive allele for brown hair. The "color modifier" E gene: E is the dominant allele that does not affect hair color expression at the "color" gene, and e is the recessive allele which changes the hair color to yellow regardless of the genotype at the "color" gene. If the following two individuals were to mate, what would be the possible PHENOTYPES (hair color) of their offspring and what would be the expected ratio of those phenotypes in their offspring?
--Male: heterozygous for the hair color gene, homozygous for the e allele.
--Female: heterozygous at both genes
Please show your work.
Explanation / Answer
Given :
Hair colour gene : B – black colour, b – brown colour
Colour modifier gene – E – no effect on hair colour expression, e – changes hair colour to yellow regardless of genotype of colour.
Male : Heterozygous for hair colour gene and homozygous for e allele
Therefore the genotype is Bbee. The possible gametes would be Be and be.
Female : Heterozygous at both genes. Therefore the genotype is BbEe. The possible gametes will have BE, Be, bE and be.
Lets make a punnet square to understand the genotypes and phenotypes in F1 generation offsprings.
Be
be
BE
BBEe
(black colour)
BbEe
(black colour)
Be
BBee
(yellow colour)
Bbee
(yellow colour)
bE
BbEe
(black colour)
bbEe
(brown colour)
be
Bbee
(yellow colour)
Bbee
(yellow colour)
Therefore the expected ration of phenotypes would be
Black colour: brown colour: yellow colour :: 3: 1: 4
Be
be
BE
BBEe
(black colour)
BbEe
(black colour)
Be
BBee
(yellow colour)
Bbee
(yellow colour)
bE
BbEe
(black colour)
bbEe
(brown colour)
be
Bbee
(yellow colour)
Bbee
(yellow colour)
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