An What are the genotypes of the man and the woman what prop

An What are the genotypes of the man and the woman? what proportions of their children will have color blindness and B blood type What proportion of their children will have color blindness and type A blood? Show calculations What proportion of their children will be colorblind and have type AB blood?

Solution

Color blindness is an X-linked recessive disease. In case of X-linked disease, females have to carry two defective genes to exhibit the phenotype, whereas males exhibit the phenotype, if they inherit one defective gene from their mother. All the males of affected mother are affected because they inherit the X-chromosome from their mother.

Human blood group is determined by multiple allele system, in which I^A and I^B are co-dominant to each other and dominant over I^O. In the given problem, the child is type “O” and the genotype is I^OI^O. The possible genotypes of father and mother are I^AI^O.

A). In this case, the mother is not affected but her father had color blindness, so, assume her genotype as xX. As the father is affected, his genotype is xY. The blood group of father is O, means genotype is IOIO and the mother’s blood group is, IAIB.

b). Cross between these two will have the progeny with the following phenotypes:

IAIB* IOIO -à IAIO (1/2), IBIO (1/2)

xX* xY -à xx (1/4, affected females), xY (1/4, affected males), xX (1/4, normal females), XY (1/4, normal males)

Thus, the proportion of children with colour blindness and B-type blood group are, ½*1/2 = ¼ or 25%

c). The proportion of children with colour blindness and B-type blood group are, ½*1/2 = ¼ or 25%

d). the proportion of children with colour blindness and AB-type blood group are,0*1/2 = 0%