Lesson Summary

• Variants of genes are called alleles.
• Genotype is the combination of alleles that an individual has for a certain gene, while phenotype is the appearance caused by the expression of the genotype.
• Incomplete dominance and codominance do not fit Mendel’s rules because one allele does not entirely mask the other.
• In polygenic inheritance, many genes control a trait with each dominant allele having an additive effect.