Final answer:
Mendelian genetics describe inheritance patterns with dominant and recessive traits, but deviations from this model include incomplete dominance, codominance, multiple alleles, sex linkage, polygenic inheritance, and epistasis, which all contribute to the complex nature of inheritance.
Step-by-step explanation:
Mendelian genetics, named after Gregor Mendel, describe inheritance patterns that follow clear dominant and recessive traits. However, there are several exceptions to Mendel's model, which include:
- Incomplete dominance: This is the case where the phenotype of the heterozygote is intermediate between the phenotypes of the homozygotes - for example, a red and white flower crossing to produce pink offspring.
- Codominance: Both alleles are fully expressed in the heterozygote without blending, such as in human blood types AB which expresses both A and B antigens.
- Multiple alleles: More than two alleles for a gene exist within a population, like blood types A, B, O which are determined by three alleles IA, IB and i.
- Sex linkage: This refers to genes located on sex chromosomes, which often result in different patterns of inheritance between males and females, such as color blindness.
- Polygenic inheritance: Traits controlled by more than one gene, which can result in a range of phenotypes, such as human skin color.
- Epistasis: This is when one gene affects the expression of another gene, such as coat color in labrador retrievers.
Such complexities explain why certain traits do not conform to simple Mendelian inheritance.