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Probability & Genetics

Probability & Genetics. Genetics & Probability. Mendel’s laws: segregation independent assortment reflect same laws of probability that apply to tossing coins or rolling dice. B. B. B. BB. Bb. b. Probability & genetics.

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Probability & Genetics

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  1. Probability & Genetics

  2. Genetics & Probability • Mendel’s laws: • segregation • independent assortment reflect same laws of probability that apply to tossing coins or rolling dice

  3. B B B BB Bb b Probability & genetics • Calculating probability of making a specific gamete is just like calculating the probability in flipping a coin • probability of tossing heads? • probability making a B gamete? 100% 50%

  4. B Bb b Probability & genetics • Outcome of 1 toss has no impact on the outcome of the next toss • probability of tossing heads each time? • probability making a B gamete each time? 50% 50%

  5. male / sperm P P PP P p P p p P p p Pp pp P female / eggs p Calculating probability Pp x Pp sperm egg offspring 1/2 x 1/2 = 1/4 1/2 x 1/2 = 1/4 + PP Pp 1/4 1/2 x 1/2 = 1/2 Pp pp 1/2 x 1/2 = 1/4

  6. P Pp p Rule of multiplication • Chance that 2 or more independent events will occur together • probability that 2 coins tossed at the same time will land heads up • probability of Pp x Pppp 1/2 x 1/2 = 1/4 1/2 x 1/2 = 1/4

  7. YyRr YyRr Yy Yy Rr Rr x x yyrr yy rr Calculating probability in crosses Use rule of multiplication to predict crosses x 1/16 ?% 1/4 1/4 x

  8. Apply the Rule of Multiplication AABbccDdEEFf x AaBbccDdeeFf AabbccDdEeFF AAxAa Aa 1/2 BbxBb bb 1/4 Got it? Try this! ccxcc cc 1 DdxDd Dd 1/2 EExee Ee 1 1/64 FfxFf FF 1/4

  9. B b Bb b B Bb 1/4 1/2 x 1/2 = 1/4 1/4 + 1/2 x 1/2 = 1/4 1/2 Rule of addition • Chance that an event can occur 2 or more different ways • sum of the separate probabilities • probability of BbxBbBb sperm egg offspring

  10. Chi-square test • Test to see if your data supports your hypothesis • Compare “observed” vs. “expected” data • is variance from expected due to “random chance”? • or is there another factor influencing data? • null hypothesis • degrees of freedom • statistical significance

  11. Any Questions??

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