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Lecture 28: Extensions to Mendelian Genetics (Alleles of the same gene can…
Lecture 28: Extensions to Mendelian Genetics
Sometimes mutations in different genes produces a similar phenotype
To uncover which gene is responsible: complementation/allelism test
Pleiotropy: A single mutation with multiple phenotypes
Alleles of the same gene can demonstrate:
Co-Dominance
Blood types based on dominant & co-dominant alleles of a single gene
Can visually see the contribution of both alleles
Semi-dominance
All three genotypes have distinct phenotypes
Dominance
Interactions between alleles of different genes:
Epistasis
A is epistatic to B if A is before B on the "pathway"
Among different genes
Quantitative (Polygenic) Traits
Two types of mutations
Gain-of-function
Almost always dominant
Loss-of-function
Weak
Conditional
Dependent on some environmental factor (enzymes depend on temperature, etc.)
Null
Usually recessive
Complementation/Allelism Test: Cross organisms with two different recessive mutations; if different genes, offspring will not show recessive trait