Question

13. A woman has type B blood and her child has type AB blood. Select the answer below that shows all of the possible blood types of the father? a. The father could be AB or A b. The father must be B c. The father must be A d. The father could be A or B e. The father could be A or O

Answer 1

Woman has type B blood and her child has type AB blood therefore the father has type A blood or type AB blood (option a is right)

[ blood group are determined by I^A, I^B , I^O alleles of I gene . Among 3 allele I^A , I^B are dominant over I^O allele. And I^A , I^B alleles are co dominant to each other.

Only homozygous I^OI^O conditions can express type O blood .

I^AI^Aand I^AI^O conditions express type A blood

I^BI^B and I^BI^O conditions express type B blood.

And only heterozygous I^AI^B conditions express AB blood type ]  

Here in this question child has AB blood i.e I^AI^B condition. woman has type B blood let assume she has I^BI^B   . The father should be I^AI^A ( A blood type) or I^AI^B (AB blood)

if father has A blood	IB ( woman's gamet)	IB (woman's gamet)
IA (man's gamet)	IAIB (AB blood)	IAIB
IA (man's gamet)	IAIB	IAIB

If father has type A blood (and mother has type B) then 100% child will be of type AB blood

If father has AB blood	IB (woman's gamet)	IB
IA (man's gamet)	IAIB (AB blood)	IAIB (AB blood )
IB	IBIB	IBIB

If father has type AB blood ( mother has type B) then there is 50% possibility of producing child of AB blood

Option b is wrong. Father cant have type B blood . If father and mother both have type B blood then child must have type B blood. Hence wrong option  

Option c is not wrong, but father must have type A blood this statement is wrong because if father has type AB blood then also there is 50% possibility of producing child with AB blood . Hence this option is not applicable . Option a is applicable .

Option d is wrong because father cant have type B blood ( though father can have type A blood)

Option e is wrong because tough father could have type A blood but father cant have type O blood if the father has type O blood then the child will be of type B blood ( as mother has type B blood and type B is dominant over type O)

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