Interaction of Genes

The phenotypic ratios obtained by Mendel in garden peas demonstrate that one gene controls one character; of the two alleles of a gene, one allele is completely dominant over the other. Due to this the heterozygote has a phenotype identical to the homozygous parent. Soon after Mendel’s work was rediscovered, instances came to light where a gene was not producing an individual effect. On the contrary, genes were interacting with each other to produce novel phenotypes which did not exhibit dominance relationships observed in Mendel’s experiments. In one of the first cases reported by Kölreuter, the heterozygote showed a phenotype intermediate between the parental phenotypes. This was termed incomplete dominance or intermediate inheritance.