In mountain rabbits, the el-1 gene is located on chromosome 3. four alleles of this gene have been identified in the population. with respect to el-1, what is the maximum number of genotypes in the progeny of a single cross between two mountain rabbits

There are four alleles of the el-1 gene; for simplicity we'll name these a, b, c and d. Assuming the parent rabbits are as diverse as possible (ab and cd), the offspring could be ac, ad, bc or bd. Ie there are a maximum of four genotypes in the progeny of a single cross between two mountain rabbits.