Which genotype is heterozygous for the C antigen?

The genotype that is heterozygous for the C antigen contains one allele that expresses the C antigen and another that does not. To assess this, it's important to understand the notation used to represent these alleles.

In the choice mentioned, the genotype DCe/dce indicates that there are two different alleles being inherited. The first part, DCe, includes the capital 'C' which indicates the presence of the C antigen. The second part, dce, includes a lowercase 'c', illustrating that it does not express the C antigen at that position. Therefore, this genotype is heterozygous for the C antigen because it possesses one C antigen allele (DCe) and one non-C allele (dce).

The other options do not demonstrate a heterozygous configuration for the C antigen. For instance, the genotype DCE/DCE is homozygous since both alleles express the C antigen. Likewise, Dce/dce and DCE/dCe entail either being homozygous or not expressing the C antigen heterozygous condition. Thus, these configurations do not meet the criteria for a heterozygous genotype for the C antigen as clearly as the chosen option does.