What are the three exceptions to Mendel's principles?

Mendel's principles, which include the laws of segregation and independent assortment, serve as foundational concepts in genetics. However, there are certain scenarios that showcase exceptions to these principles, one of which includes codominance, incomplete dominance, and environmental factors.

Codominance occurs when both alleles of a gene are fully expressed in the phenotype, such as in blood types, where both A and B alleles can be present. Incomplete dominance refers to a situation where the phenotype of heterozygotes is intermediate between the phenotypes of the homozygotes, exemplified by the blending of colors in certain flower varieties.

Additionally, environmental factors can influence the expression of genes, illustrating how the phenotype may not solely conform to Mendelian ratios due to external conditions. For instance, temperature can affect the coloration of Siamese cats, demonstrating how environment interacts with genetics.

The other sets of terms provided do not serve as exceptions to Mendel's principles in the same way. Genetic drift, mutation, and selection relate to evolutionary processes, while environmental stressors, hybrid vigor, and epistasis pertain to broader genetic and ecological interactions. Penetrance, expressivity, and linkage disequilibrium delve into genetic variation and inheritance patterns rather than directly opposing