1. Multiple Alleles and Polygenic Traits

2. when more than two different alleles exist for the same trait.
Multiple Alleles:
when more than two different alleles exist for the same trait.
(Remember: each individual will only have two alleles for a trait but there are several alleles to choose from.)

3. Rabbits, coat color
In rabbits, coat color is controlled by multiple alleles.
Full color (C), white (c), light-gray or chinchilla (cch) and white with black points or a Himalayan (ch). Full color is dominant to all the other alleles. Chinchilla is dominant to Himalayan and white.

5. Cross a heterozygous Chinchilla
(cchc) with a heterozygous full color with himalayan (Cch).
cchc x Cch

6. cch c C ch

7. cch c C
Ccch ch

8. cch c C
Ccch Cc ch

9. cch c C
Ccch Cc ch
cchch

10. cch c C
Ccch Cc ch
cchch
chc

11. Genotypic Ratios:
1 Ccch: 1Cc : 1 cchch: 1 chc
Phenotypic Ratios:
2 full color: 1 Chinchilla: 1 Himalayan

12. In humans, blood type has multiple alleles
In humans, blood type has multiple alleles. IA and IB are codominant and i (type O blood) is recessive.

13. Blood Type
Type of Antigen
Possible Genotypes
Type A
Type B
Type AB
Type O

14. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
Type B
Type AB
Type O

15. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
Type AB
Type O

16. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
B antigen
Type AB
Type O

17. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
B antigen
IBIB, IBi
Type AB
Type O

18. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
B antigen
IBIB, IBi
Type AB
A and B antigens
Type O

19. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
B antigen
IBIB, IBi
Type AB
A and B antigens
IAIB
Type O

20. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
B antigen
IBIB, IBi
Type AB
A and B antigens
IAIB
Type O
No antigens

21. Blood Type
Type of Antigen
Possible Genotypes
Type A
A antigen
IAIA, IAi
Type B
B antigen
IBIB, IBi
Type AB
A and B antigens
IAIB
Type O
No antigens ii

22. Cross a heterozygous type A with a heterozygous type B.
IAi x ___

23. Cross a heterozygous type A with a heterozygous type B.
IAi x IBi

24. IA i IB

25. IA i IB
IAIB

26. IA i IB
IAIB
IBi

27. IA i IB
IAIB
IBi
IAi

28. IA i IB
IAIB
IBi
IAi ii

29. Genotypic Ratios:
1 IAi : 1 IAIB : 1 IBi : 1 ii
Phenotypic Ratios:
1 Type A: 1 Type AB: 1 Type B: 1Type O

30. Cross a person with type AB blood with another person with type O blood.
IAIB x ___

31. Cross a person with type AB blood with another person with type O blood.
IAIB x ii

32. IA IB i

33. IA IB i
IAi

34. IA IB i
IAi
IBi

35. IA IB i
IAi
IBi

36. IA IB i
IAi
IBi

37. 2 IAi : 2 IBi Genotypic Ratios: Phenotypic Ratios:
2 Type A: 0 Type AB: 2 Type B: 0 Type O

38. Polygenic Inheritance:
the inheritance pattern is controlled by two or more genes each with two alleles.

39. In humans, eye color is the result of polygenic inheritance.
At the present, three gene pairs controlling human eye color are known.
Two of the gene pairs occur on chromosome pair 15 and
one occurs on chromosome pair 19.

40. Humans, eye color
The bey 2 gene, on chromosome 15, has a brown and a blue allele
A second gene, located on chromosome 19 (the gey gene) has a blue and a green allele.
A third gene, bey 1, located on chromosome 15, is a central brown eye color gene.

41. Blue eyes will occur only if all four alleles are for blue eyes.
The brown allele is always dominant over the blue allele so even if a person is heterozygous (one brown and one blue allele) for the bey 2 gene on chromosome 15 the brown allele will be expressed.
The gey gene also has two alleles, one green and one blue. The green allele is dominant to the blue allele on either chromosome but is recessive to the brown allele on chromosome 15.
This means that there is a dominance order among the two gene pairs. If a person has a brown allele on chromosome 15 and all other alleles are blue or green the person will have brown eyes.
If there is a green allele on chromosome 19 and the rest of the alleles are blue, eye color will be green.
Blue eyes will occur only if all four alleles are for blue eyes.

42. Polygenic inheritance usually shows up as a range of variation such has height, skin color or hair color.
The results of an average population will result in a bell-shaped curve.

44. Phenotype = genotype + environment