1. Probability and Punnett Squares
Genotype: the combination of alleles for a give trait (ex. Tt)
Phenotype: the appearance of a trait as determined by its genotype (ex. Tall)
Homozygous: two of the same alleles (TT, tt)
Heterozygous: two different alleles (Tt)

2. Independent Assortment
Genes from different traits can segregate independently during the formation of gametes

3. 2 Trait Cross Dihybrid “The Double Cross”
Let’s examine the following pea plant traits:
T=tall; t=short
F=purple; f=white
Cross a plant that is homozygous dominant for both traits with a plant that is homozygous recessive for both traits
What are the percentages of genotypes? Phenotypes?

4. TT FF x tt ff TF tf
TtFf

5. Cross 2 plants that are both heterozygous for both traits.

6. Cross 2 plants that are both heterozygous for both traits.
What are the genotypes of the parents?
Heterozygous for both traits.
Tt Ff x Tt Ff
What are the possible combination of genes the parent can pass on to the offspring?
(FOIL)
TF, Tf, tF, tf

7. Cross 2 plants that are both heterozygous for both traits.

8. Cross 2 plants that are both heterozygous for both traits.TF Tf tF tf

9. Cross 2 plants that are both heterozygous for both traits.TF Tf tF tf
TTFF
TTFf
TtFF
TtFf
TTff
Ttff
ttFF
ttFf
ttff

10. Cross 2 plants that are both heterozygous for both traits.TF Tf tF tf
TTFF
TTFf
TtFF
TtFf
TTff
Ttff
ttFF
ttFf
ttff

11. Cross a male who is heterozygous for both traits with a female who is homozygous recessive for fur color and heterozygous for coat texture. B=black; b=white and R=rough; r=smooth

12. Beyond Dominant and Recessive Alleles

13. Incomplete Dominance One allele is not dominant over another.
The heterozygous phenotype is somewhere in between the two homozygous phenotypes.
Example: CRCR = red
CWCW = white
CRCW = pink

14. Codominance Both alleles contribute to the phenotype.
Example: B = black
W = white
BB = black WW = white BW = speckled

18. Multiple Alleles
More than 2 alleles exist in a population

19. Human Blood Type

20. Polygenic Trait Traits controlled by 2 or more genes.
Example human eye color and skin color