Extensions of Mendelian Analysis

1
Extensions of Mendelian Analysis

• Modifications of Mendelian Ratios
• Single Gene modifications
• Two gene pair modifications modified 9331
  ratios
• Modification of Expression

2
Single Gene modifications

• Incomplete dominance (partial dominance)
• Multiple alleles
• Lethal alleles

3
Incomplete dominance (partial dominance)

• Expression of a heterozygous phenotype that is
  distinct from and usually intermediate to either
  homozygous phenotype

4
Incomplete dominance (partial dominance)
Tay Sachs and Sickle Cell Anemia Heterozygous
are intermediate at the biochemical level.
5
Multiple Alleles Co-Dominance
6
Bombay phenotype

• H allele affected
• Recessive epistasis
• Show O phenotype
• Genotype variable

7
Lethal alleles

• Yellow dominant to Agouti coat color
• No purebred yellow
• Deletion mutation
• Recessive for lethality

8
Two gene pair modifications modified 9331
ratios

• Epistasis
• Suppression
• Complementary gene action

9
Recessive Epistasis
10
Dominant Epistasis
11
Suppression
12
Complementary gene action
13
Complementary gene action
14
Modification of Expression

• Pleiotropic effects
• Penetrance and Expressivity

15
Pleiotropic effects
16
Penetrance
No expression
17
Expressivity