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Probability and Genetics

Probability and Genetics. Fruit Fly Color and Probability. 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. Sample Punnett Square 1.

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Probability and Genetics

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  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.

  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. Sample Punnett Square 3 • Offspring have several possibilities in this case • 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.

  9. Sample Punnett Square 3 • Now let’s explore the probability of genotypes • 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

  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

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