Production of more antigen in the homozygous state than in the heterozygous state is referred to as which term?

• A. Dosage effect
• B. Allelic expression
• C. Antigen amplification
• D. Gene dosage

Answer: (A)

The main idea is that the amount of an antigen on red cells can depend on how many copies of the antigen gene are present. When someone is homozygous for a given antigen gene (two copies), more antigen sites are produced than in someone who is heterozygous (one copy). This difference in antigen density is called the dosage effect. It explains why some antibodies react more strongly with cells from homozygous individuals than with cells from heterozygous individuals. While gene dosage refers to the actual number of gene copies, the specific phenomenon affecting antigen quantity on the cells due to zygosity is the dosage effect. Allelic expression would imply preferential expression of one allele rather than a quantitative difference tied to homozygosity, and antigen amplification isn’t the standard term used here.