1. Extensions of Mendelian Analysis
Modifications of Mendelian Ratios
Single Gene modifications
Two gene pair modifications: modified 9:3:3:1 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 9:3:3:1 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