1. When Heredity Follows Different Rules
Chapter 12.2 pg
When Heredity Follows Different Rules

2. Up to now, every genetics problem we have done has fit this pattern
Simple Mendelian Inheritance- trait with 2 alleles (one dominant and one recessive)
Up to now, every genetics problem we have done has fit this pattern
But………….

3. Things are about to Change!

4. Incomplete Dominance-
heterozygous individuals show an intermediate phenotype

5. Incomplete Dominance
RED Flower x WHITE Flower ---> PINK Flower

6. R = allele for red flowers W = allele for white flowers RW = genotype for pink flowers

8. Codominance
equal expression of both alleles at the same time

9. Codominance
Black x White --- Checkered

10. Codominant feather colors

11. R = allele for red feathers W = allele for white feathers RW = genotype for red and white feathers

12. Practice Problem (incomplete dominance)
What would the genotypic and phenotypic ratios be of the offspring when crossing two pink flowers together?

13. Practice Problem (Codominance)
What would the genotypic and phenotypic ratios be of the offspring when crossing checkered chickens together?

14. Practice Problem (incomplete dominance)
What would be the result of crossing a homozygous white flower with a heterozygous pink flower?

15. Sex Determination 22 pairs of homologous chromosomes called Autosomes
*remember: humans have 46 chromosomes
22 pairs of homologous chromosomes called Autosomes
1 pair of Sex Chromosomes
XX = female, XY = male

16. Sex determination

17. Sex-Linked Inheritance
Traits that are located on a sex chromosome (x or y)
Will affect a certain sex more often

18. Sex-linked example
b = bald
B = not bald

19. Polygenic Inheritance
Trait controlled by many genes (more than 2)
Gives a wide range of traits
Example genotype: AaBBCCDd

20. Polygenic Inheritance

21. Multiple Alleles
Trait controlled by more than 2 alleles of a single gene

22. BA: Ash Red, B: Blue, b: Chocolate
Multiple Alleles
Example:
Feather color in pigeons
BA: Ash Red, B: Blue, b: Chocolate

23. BA: Ash Red

24. B: Blue

25. b: Chocolate

26. Human blood type: codominance and multiple alleles

27. A B AB IAIB IBIBor IBi IAIA or IA i A and B None Genotypes
Surface Molecules
Phenotypes
IAIA or IA i A
IBIBor IBi B
IAIB
A and B AB ii
None O

28. Practice Problem (Codominance and multiple alleles)
A man who is type A is accused of fathering 2 children. One of the kids has type O blood and the other has type B. The mother has type B. Could this man be the father of both children? Prove your answer using punnett squares.