The H substance is needed for the proper phenotypic expression of the A, B, and AB blood types in the ABO blood typing system in humans. Individuals who are recessive for the H substance (hh) will have a type O phenotype, even if they have the A and/or B alleles. Two individuals, each with type AB blood and heterozygous at the H locus have children. What is the probability they will have a child who is phenotypically type O?

The correct answer is - 4/16.

Explanation:

In this question, it is stated that in ABO blood system the proper phenotypic expression of A, B, AB blood types needs H substance. If an individual has recessive for the H substance (hh) will have a type O phenotype.

The cross: ABHh and ABHh

gametes: two set of AH, BH, Ah, Bh

Punnett:

         AH         BH          Ah          Bh

AH    AAHH   ABHH     AAHh     ABHh

BH    ABHH   BBHH     ABHh     BBHh

Ah    AAHh    ABHh     AAhh      ABhh

Bh    ABHh    BBHh     ABhh      BBhh

As shown there is only 4 out of 16 offspring are recessive for H substance therefore, only 4/16 will have O blood group

b is the answer and if you need further with anything message me

the law of original horizontality explains:   why rocks appear in layers. correct answer: b the law suggests that all rock layers are originally laid down (deposited) horizontally and can later be deformed.   the principle is used by geologists to make assumptions about the relative ages of sedimentary rocks.