1. 5.5
Incomplete Dominance
a condition in which the alleles are neither dominant nor recessive
results in a blending of traits

2. Incomplete Dominance examples
red flowers crossed with white flowers produce pink flowers
brachydactyly

3. Codominance
both alleles are expressed with no blending

4. Codominance examples roan horses both white & red hairs
Andalusian chickens
both black & white feathers

5. Multiple Alleles one of several alleles can be at a given locus
example: human blood types

6. Dominant Alleles Recessive Allele
IA and IB
Recessive Allele i

7. Human Blood Types IA IA type A blood IA i type A IB IB type B
IB i type B
IA IB type AB
i i type O

8. Dihybrid Cross deals with two sets of traits at the same time
example: dealing with plant height (tall/short) AND pea color (yellow/green) in the same cross

9. Independent Assortment
The separation of one set of alleles during gamete formation is not affected by the separation of another set of alleles.
background: PressArt - Biology text book p.101

10. Polygenic Inheritance
two or more genes affecting the same trait
example: human skin color

11. Sex-Linked Traits 5.6 autosomes sex chromosomes
non-sex-determining chromosomes
humans = 22 pairs
sex chromosomes
XX = female
XY = male

12. Female = XX
Male = XY X X X X X X X Y Y X Y X

13. Sex-Linked Traits Some genes are carried on the sex chromosomes.
X and Y chromosomes are not homologous.
If there is a defective gene on X, the Y would not have a normal gene to counteract it.

14. Sex-Linked Traits
indicated with a superscript above the X and Y chromosomes
examples:
XH Xh
XH Y

15. Sex-Linked Traits hemophilia human blood disorder
lack of a blood chemical that allows for blood clotting

16. Hemophilia XH Xh carrier female
a heterozygous female that does not have the disease but does carry the gene for the trait

17. Hemophilia XH Xh carrier female XH XH normal female XH Y normal male
Xh Xh hemophiliac female
Xh Y hemophiliac male