2: Non-Mendelian inheritance
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- 2.1: Co-dominance and Incomplete Dominance
- In complete dominance, only one allele in the genotype is seen in the phenotype. In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype.
- 2.2: Multiple alleles, incomplete dominance, and codominance
- In the real world, genes often come in many versions (alleles). Alleles aren't always fully dominant or recessive to one another, but may instead display codominance or incomplete dominance.
- 2.3: Pleiotropy and lethal alleles
- Pleiotropy: where one gene affects multiple characteristics. Lethal alleles: alleles that prevent survival when homozygous or heterozygous.
- 2.4: Polygenic inheritance and environmental effects
- Traits that are controlled by multiple genes and/or influenced by the environment. Penetrance and expressivity.
Thumbnail: Incomplete dominance in snapdragons. (CC BY-NC-SA / cropped from original; Khan Academy).