1. Alleles segregate during gamete formation, but do they do it independently?

2. Two-factor Cross, F1 RRYY x rryy Round/yellow peas wrinkled/green
What will offspring look like?
Gives hybrid plants needed for next cross

3. Two-Factor Cross, F2
RrYy x RrYy

4. Independent Assortment
Genes for different traits can segregate independently during the formation of gametes.
Leads to genetic variation in plants, animals, and other organisms.

5. Not all genes show simple patterns of dominant and recessive
Incomplete dominance
Codominance
Multiple alleles
Polygenic traits
Sex-linked

6. Incomplete Dominance RW One allele NOT dominant over another
Four o’clock plants
RR x WW RW

7. Codominance Both alleles contribute to the phenotype
Chicken: black feathers codom with white
Heterozygous = erminette (speckled)
Humans: protein controlling cholesterol levels
Blood type

8. Many genes have more than 2 alleles Coat color in rabbits
Multiple Alleles
Many genes have more than 2 alleles
Coat color in rabbits
Human gene for blood type

12. Polygenic Traits Traits controlled by two or more genes
At least three genes involved in reddish-brown pigment in eyes of fruit flies
Different combinations of alleles produce different eye colors
Polygenic traits often show a wide range of phenotypes
Skin color in humans partly because more than four different genes probably control this trait

13. Sex-linked Genes