A true-breeding black rabbit is crossed with a true-breeding brown rabbit. All o

Question

A true-breeding black rabbit is crossed with a true-breeding brown rabbit. All of the F1 rabbits are black. Two of these black F1 rabbits were crossed together and produced exactly two offspring. What is the probability that both offspring were black? Assume that color is controlled by a single autosomal gene.

In a species of tree, seed color is determined by four independently assorting genes: A, B, C, and D. The wild-type alleles are: A+, B+, C+, and D+. The mutant alleles are all lof and are A, B, C, and D. The lof alleles are unable to work as well. This pathway is diagrammed as shown below. When both red and blue pigments are present, the seeds are purple. Trees with the genotypes A+A-B+B-C+C-D+Dand A+A-B+B-C+C-D-D- were crossed.

a) What color are the seeds of these two parental genotypes?

(b) Determine what color offspring seeds are and in what proportions

26. In a species of tree, seed color is determined by four independently assorting genes: A, B, C, and D. The wild-type alleles are: A+,B+,C+,and D+. The mutant alleles are all lof and are A-,B-, C-, and D- The lof alleles are unable to work as well. This pathway is diagrammed as shown below. When both red and blue pigments are present, the seeds are purple. Trees with the genotypes A+A-B+B-C+C-D+D. and A+A-B+B-C+C-D-D- were crossed White precursorYellowOrangeRed Blue (a) What color are the seeds of these two parental genotypes? (b) Determine what color offspring seeds are and in what proportions

Explanation / Answer

1. Let the gene responsible for black color be B and for brown color be b.

Genotype of true breeding black rabbit is BB

Genotype of true breeding brown rabbit is bb.

A cross between these two individuals will produce all off springs having genotype Bb. Since this generation is black so the B gene is dominant over b.

When F1 generation is crossed, it will produce 1 true breeding BB offspring, 2 Bb offspring and 1 true breeding bb offspring.

So the chance of getting a black offspring is 75%.

Here only two offsprings are produced according to question, so the probabilty of having both offspring black will be 75÷2= 37.5%.

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