Probability and Genetics
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Transcript of Probability and Genetics
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Probability and Genetics
Fruit Fly Color and Probability
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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)
Grey Black
Genotype (gene makeup)
GG, Gg gg
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Sample Punnett Square 1
Cross a homozygous grey fly (GG) with a homozygous black fly (gg)
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Sample Punnett Square 1
All offspring are phenotype grey and genotype Gg
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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)
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Sample Punnett Square 2
Cross a heterozygous grey fly (Gg) with a homozygous black fly (gg).
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Sample Punnett Square 1
Offspring have two possibilities in this case
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Grey (Gg) Black (gg) Each outcomes happens 2 times
out of 4 = 50% chance
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Sample Punnett Square 3
Cross two heterozygous grey flies (Gg)
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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
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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
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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