 | Study Outline
(See related pages)
- Inheritance patterns of single genes
- Recessive alleles often cause a reduction in the amount or function of the encoded protein
- Mutations that cause a loss of function in an essential gene result in a lethal phenotype
- Incomplete dominance occurs when two alleles produce an intermediate phenotype
- Some genes exist as three or more different alleles
- Alleles of the abo blood group can be dominant, recessive, or codominant
- Certain genes exhibit a gene dosage effect
- Overdominance occurs when heterozygotes have superior traits
- Dominant traits can skip a generation due to incomplete penetrance
- The expression of a trait can be influenced by the environment
- The outcome of certain traits can be influenced by the sex of the individual
- Gene interactions
- A cross involving a two-gene interaction can produce a 9:3:3:1 ratio in offspring when four distinct phenotypes are produced
- A cross involving a two-gene interaction can produce a 9:7 ratio when both genes are epistatic to each other
- Bridges observed an 8:4:3:1 ratio because the cream-eye allele can modify the eosin-eye allele, but not the red or white alleles
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