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Unformatted text preview: 1 Next topic: Probability • Last lecture: – http://www.esf.edu/efb/powell/inheritance1.pdf – Or go to my homepage, click on teaching, under Genetics click on inhertance1 Calculating genetic ratios • use two statistical rules – commit to memory Product rule: • The probability of independent events occurring together is the product of the probabilities of each individual event. Dice example • probability of rolling double sixes? • first, what is the P of a single 6? • 1/6 • P of two 6’s, 1/6 x 1/6 = 1/36 • Therefore, if you rolled the two dice 3,600 times, you should get double sixes in about 100 of the rolls. Sum rule • The probability of either of two mutually exclusive events occurring is the sum of their individual probabilities. Dice example • P of rolling a 7 with two dice? 2 die #1 die #2 P 6 1 1/6 x 1/6 = 1/36 die #1 die #2 P 6 1 1/6 x 1/6 = 1/36 1 6 1/6 x 1/6 = 1/36 5 2 1/6 x 1/6 = 1/36 2 5 1/6 x 1/6 = 1/36 4 3 1/6 x 1/6 = 1/36 3 4 1/6 x 1/6 = 1/36 die #1 die #2 P 6 1 1/6 x 1/6 = 1/36 1 6 1/6 x 1/6 = 1/36 5 2 1/6 x 1/6 = 1/36 2 5 1/6 x 1/6 = 1/36 4 3 1/6 x 1/6 = 1/36 3 4 1/6 x 1/6 = 1/36 sum rule 6/36 = 1/6 die #1 die #2 P 6 1 1/6 x 1/6 = 1/36 1 6 1/6 x 1/6 = 1/36 5 2 1/6 x 1/6 = 1/36 2 5 1/6 x 1/6 = 1/36 4 3 1/6 x 1/6 = 1/36 3 4 1/6 x 1/6 = 1/36 sum rule 6/36 = 1/6 Therefore, out of 3,600 rolls, about 600 will be a seven. Application to genetics • gene pairs – A produces anthocyanin (bluered pigment) – a  no anthocyanin – Y  normal green leaves – y  yellowgreen leaves – P  normal pollen formation – p  male sterile (no pollen) Cross heterozygotes • AaYyPp x AaYyPp • What is the P of getting a homozygous recessive in all gene pairs? (aayypp) • First treat each trait separately, then apply the product rule • gene pairs – A produces anthocyanin (blue red pigment) – a  no anthocyanin – Y  normal green leaves – y  yellowgreen leaves – P  normal pollen formation – p  male sterile (no pollen) 3...
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This note was uploaded on 04/09/2008 for the course EFB 307 taught by Professor Powell during the Fall '07 term at Syracuse.
 Fall '07
 powell

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