The A and B antigens in humans may be found in water-soluble form in secretions, including saliva, of some individuals (Se/Se and Se/se) but not in others (se/se). The population thus contains 'secretors' and 'nonsecretors.' How will the results of such matings change if both parents are heterozygous for the gene controlling the synthesis of the H substance (Hh)?

Key Concepts

H Substance and ABO Blood Group System

The H substance is a precursor to the A and B antigens in the ABO blood group system. Individuals with at least one dominant H allele (Hh or HH) can produce the H substance, which is necessary for the synthesis of A and B antigens. Those with the homozygous recessive genotype (hh) cannot produce H substance and thus cannot express A or B antigens, leading to blood type O.

Secretor Status

Secretor status refers to the ability of individuals to secrete blood group antigens into bodily fluids, such as saliva. This trait is determined by the Se gene, where individuals with at least one dominant allele (Se/Se or Se/se) are classified as 'secretors' and can produce soluble forms of A and B antigens, while those with the recessive genotype (se/se) are 'nonsecretors' and do not secrete these antigens.

Punnett Square and Genetic Crosses

A Punnett square is a tool used to predict the genotypes of offspring from a genetic cross. In this scenario, both parents are heterozygous for the H substance gene (Hh), which allows for a variety of combinations in their offspring. By setting up a Punnett square, one can determine the probabilities of different genotypes and phenotypes, including the potential for secretor and nonsecretor status in the offspring.