Probability and Genetics Fruit Fly Color and Probability

Fruit Flies l The body color in fruit flies is controlled by two alleles – – l 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) Genotype (gene makeup) Grey Black GG, Gg gg

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

Sample Punnett Square 1 l All offspring are phenotype grey and genotype Gg l l 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)

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

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

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

Sample Punnett Square 3 l Offspring have several possibilities in this case l l l Grey (Gg or GG) Black (gg) First explore phenotypes – – l 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 l Now let’s explore the probability of genotypes l Gg happens 2 out of 4 times = 50% GG happens 1 out 4 times = 25% gg happens 1 out of 4 times = 25% l For the whole example: l l – – – 25% chance of Black (gg) flies 25% chance of Grey (GG) flies 50% chance of Grey (Gg) flies

Probability l l l 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