You are studying the inheritance of genes controlling tail size and fur color in

ID: 52292 • Letter: Y

Question

You are studying the inheritance of genes controlling tail size and fur color in squirrels. Based on past observations, it is known that the long tail allele is dominant (L) and the short tail allele is recessive (l), as well as that grey fur color is dominant (G) and brown fur color is recessive (g). Assuming that these genes assort independently, answer the following questions. (5 points)

A) Cross 1: You cross a squirrel that is homozygous for both the long tail and brown fur color alleles to a squirrel that is homozygous for both the short tail and grey fur color alleles. Write out the parent genotypes of this cross:

Cross1: ____________________________________________ X ______________________________________

B) What is the phenotype and genotype of the F1 progeny?

____________________________________________________________________________________________

C) Cross 2: You next testcross the F1 progeny. Write out the genotypes of this cross:

Cross 2: ____________________________________________ X ______________________________________

D) Write out and fill in a Punnet square for Cross 2 to determine the progeny phenotype and genotype ratios. Make sure to show your work for the Punnet square and clearly indicate the progeny ratios.

Explanation / Answer

(A) LLgg ( parent who is homozygous for both the long tail and brown fur color alleles) * llGG (parent who is homozygous for both the short tail and grey fur color alleles)

(B) LlGg - genotype of F1 progeny; Phenotype- Squirrel with Long tail and Grey fur

Hence, Cross2- LlGg * llgg

(D) LlGg * llgg.......................parents

LG, Lg, lG,lg lg ........................gametes

LlGg/llgg

LlGg

Long tail, grey fur

Llgg

Long tail, brown fur

llGg

short tail, grey fur

llgg

short tail, brown fur

Phenotypic ratio = Long tail, grey fur: Long tail, brown fur: short tail, grey fur: short tail, brown fur = 1:1:1:1

Genotypic ratio= LlGg: Llgg: llGg: llgg = 1:1:1:1