Question

12. What is a suspected heterozygous individual crossed with in a test cross?

A. Homozygous dominant

B. Homozygous recessive

C. Heterozygous dominant

D. Heterozygous recessive

13. Which of the following genotypes is possible in the offspring of a homozygous male with blood group A and a female with blood group B?

Α. ΙΑΙΑ

The answers are 12B, 13B, 14C can you explain how?

Answer 1

12) test cross is done to determine the genotype of the individual if the individual shows a recessive phenotype the genotype of the individual is homozygous recessive, but for the individuals showing dominant phenotype, it can be either homozygous dominant or heterozygous, the individual is crossed with a homozygous recessive individual.

If the individual is homozygous dominant all the progenies of the test cross will show dominant phenotype if the individual is heterozygous progenies with both dominant and recessive phenotype can be obtained.

so the answer is B) homozygous recessive.

13) male is homozygous with A type blood, so its genotype is IAIA, the female has B type blood so her genotype can be either IBIB or IBi.

if the genotype is IBi

IAIA * IBi

	IB	i
IA	IAIB	IAi

so the possible genotypes are IAIB and IAi so the answer is B) IAi.

14) here males are affected, and females are carriers, for sex lined recessive traits, the females have two X chromosomes, so if the female is heterozygous they are carriers but not affected, males inherit X chromosome from mother so sons of carrier females are affected, here sons of carrier females are affected so the answer is C) X -linked recessive.