Dental Admissions Test (DAT) Practice Test

The Bombay phenotype is a rare blood type characterized by the absence of A, B, and H antigens in individuals who have inherited A and B alleles from their parents. This occurs due to a mutation in the H gene, which is responsible for producing the H antigen that is required for the functioning of the A and B antigens. This phenomenon is an example of epistasis, which is a type of gene interaction where the expression of one gene is dependent on the expression of another gene. In this case, the H gene is epistatic to the A and B genes, as its expression is necessary for the production of A and B antigens. Therefore, options B, C, and D are incorrect as they do not explain the specific gene interaction observed in the Bombay phenotype.