Question

The two genes f and g, code for body size and aggressiveness, respectively. The F allele is dominant over f, and codes for a larger body size. The G allele is dominant over g, and codes for more aggressive ants. You perform a Mendelian dihybrid cross (NOT a test cross) on these traits. If there is no recombination between these genes (recombination frequency = 0.00), what ratio should you see phenotypes in in the offspring? (note that the parent generation was made up of large aggressive ants and small docile ants.)

		A. 9 large aggressive:3 large docile:3 small aggressive: 1 small docile
		B. 1 large aggressive:1large docile:1small aggressive:1small docile
		C. 12 large aggressive:4 small docile (i.e. 3 large aggressive:1small docile)
		D. None of the above

Answer 1

Answer: Choice C

Explanation: According to the information, a Mendelian cross is performed between two parents obtained after crossing the parents and the F2 is noticed. This suggests that the parents or P generation was homozygous i.e. AA and aa in nature. This gives that all the F1 generation was Aa in nature. The selfing of the F1 would bear following Punnett square:

	A	a
A	AA	Aa
a	Aa	aa

Genotype: AA: Aa: aa :: 1:2:1

Phenotype: Dominant: recessive :: 3:1

This gives that choice C is the correct answer.