F₂ Analysis
How is the horns trait inherited?

The total number of progeny in the F₂ generation is 93. The F₁ progeny of a cross of an individual with two horns and an individual with no horns all had one horn, that is, a phenotype intermediate between the two parental phenotypes.

The simplest hypothesis is that the horn trait exhibits incomplete dominance with a single gene involved. The homozygous genotypes give the two-horns and no-horn phenotypes, while the heterozygous genotype gives the one- horn phenotype.


If we use h for the horns allele and H for the no-horn allele, we can follow the cross.

Let us first study the parental cross of the two-horned MendAlien with the no-horned MendAlien.