Question

For the following: 1) Identify the genotypes of the parents 2) Complete a Punnett Square & 3) Give the genotypic AND phenotypic results of the cross (percentage OR ratio)

Problem:

In humans, blood type is controlled by multiple alleles – A, B & O.

Show the cross between a male with Type O blood and a woman with Type AB blood.

What blood types will NOT show up in their offspring?

(Please write or type response, do not use cursive writing due to visual impairment)

Thank you.

Answer 1

ABO blood group system is an example of codominance where alleles A and B are completely dominant over O allele but when allele A and B are present together, expression of both the alleles takes place that means none of them act as a dominant or recessive.

So, AA or AO will give - A blood group

BB or BO will give - B blood group

AB - AB blood group

OO - O blood group

1) Here, in the question, cross between a male with O blood type and a female with AB blood type takes place.

Hence the genotypes of parents are-

Male- OO ; Female ; AB

2) Punnet square for the above cross

AB/OO	O	O
A	AO	AO
B	BO	BO

3 ) The genotypic ratio of the offsprings is :-

AO : BO = 1 : 1

The phenotypic ratio of the offsprings is :-

A blood type : B blood type = 1 : 1

4) AB blood type and O blood type are not possible in the offsprings because for AB and O blood group, the genotypes must be AB and OO, respectively, and these genotypes are not possible with the given cross (OO x AB).