1. Probability and Genetics Fruit Fly Color and Probability

2. Fruit Flies The body color in fruit flies is controlled by two alleles – Grey is dominant and represented by G – Black is recessive and represented by g The phenotypes of the flies follow the chart below. Phenotype (color) GreyBlack Genotype (gene makeup) GG, Gggg

3. Sample Punnett Square 1 Cross a homozygous grey fly (GG) with a homozygous black fly (gg)

4. Sample Punnett Square 1 All offspring are phenotype grey and genotype Gg So 4 out of 4 possible outcomes have genotype Gg and phenotype grey There is a 100% possibility that the offspring will be Grey (Gg)

5. Sample Punnett Square 2 Cross a heterozygous grey fly (Gg) with a homozygous black fly (gg).

6. Sample Punnett Square 1 Offspring have two possibilities in this case Grey (Gg) Black (gg) Each outcomes happens 2 times out of 4 = 50% chance

7. Sample Punnett Square 3 Cross two heterozygous grey flies (Gg)

8. Grey (Gg or GG) Black (gg) First explore phenotypes – Grey happens 3 out of 4 times = 75% – Black happens 1 out of 4 times = 25% There is a 75% possibility the offspring will be grey and a 25% possibility they will be black. Sample Punnett Square 3 Offspring have several possibilities in this case

9. Gg happens 2 out of 4 times = 50% GG happens 1 out 4 times = 25% gg happens 1 out of 4 times = 25% For the whole example: – 25% chance of Black (gg) flies – 25% chance of Grey (GG) flies – 50% chance of Grey (Gg) flies Sample Punnett Square 3 Now let’s explore the probability of genotypes

10. Probability The concept of probability and genetics goes outside of just flies For your project you will analyze the probability for eye color Use the same techniques used for flies