Question

You must record all crosses and results on the log sheets provided in this lab. Your completed log sheets must be attached to your final report as an Appendix. PART IV: POST-LAB. These following exercises must be completed in your labreport: 1. Length of fur is also genetically determined. The allele L produces long fur and its corresponding allele, I produces short fur. Long fur is dominant to short. a) You mate 2 hamsters. Both heterozygous for brown long fur. Would you expect any of the offspring to have black short fur? If so, what proportion would have black short fur? b) What proportion would have black long fur? 2. In cats, yellow coat color is due to a gene, b, and black coat color is due to its allele, B. The alleles b and Bare sex-linked (i.e. are located on the X chromosome). Because of Barr body formation, the heterozygous condition results in tortoise shell colored cats (both black and yellow patches) a) What kinds of offspring would be expected from the mating of a black male with a yellow female? b) Of a yellow male with a tortoise female?

Answer 1

1) both hamsters have brown long fur and both of them are heterozygous for the trait, so the brown is dominant to black fur and long tail is dominant to short fur.

Let the alleles be L- long fur, l-short fur, B- brown fur, b- black fur

LlBb * LlBb

	LB	Lb	lB	lb
LB	LLBB ( brown, long fur)	LLBb( brown, long fur)	LlBB( brown, long fur)	LlBb( brown, long fur)
Lb	LLBb( brown, long fur)	LLbb ( black, long fur)	LlBb ( brown, long fur)	Llbb ( black, long fur)
lB	LlBB( brown, long fur)	LlBb( brown, long fur)	llBB ( brown, short fur)	llBb( brown, short fur)
lb	LlBb( brown, long fur)	Llbb ( black, long fur)	llBb( brown, short fur)	llbb ( black, short fur)

a) yes.proportion of black short fur= number of progeny with black, short fur/total number of progeny=1/16

b) The proportion of progeny with black long fur= number of progeny with black, long fur/total number of progeny=3/16