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

Answer 1

A true-breeding black rabbit is crossed with a true-breeding brown rabbit. All of the F1 rabbits are black.

This tells you black (B) is dominant over brown (b). So, the cross was BB x bb: Bb Bb Bb Bb. All heterozygous dominant and you see them all 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.

You can cross two F1 rabbits to know the probabilities of the offspring, Bb x Bb: BB Bb bB bb you have 25% chances of having brown rabbits.

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.

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

Don't has the diagram to know the colors, but you could see the ABCD alleles to answer that.

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

(A+A-)(B+B-)(C+C-)(D+D-) x (A+A-)(B+B-)(C+C-)(D-D-)=

(A+A+)(B+B+)(C+C+)(D+D-)

(A+A-)(B+B-)(C+C-)(D+D-)

(A-A+)(B-B+)(C-C+)(D-D-)

(A-A-)(B-B-)(C-C-)(D-D-)