52 ch13probability2007

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52 ch13probability2007

  1. 1. Probability & Genetics AP Biology 2006-2007
  2. 2. Genetics & Probability  Mendel’s laws: segregation  independent assortment  reflect same laws of probability that apply to tossing coins or rolling dice AP Biology
  3. 3. 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? B 100% BB B  AP Biology B 50% Bb b
  4. 4. Probability & genetics  Outcome of 1 toss has no impact on the outcome of the next toss probability of tossing heads each time? 50%  probability making a B gamete each time? 50%  B Bb b AP Biology
  5. 5. Calculating probability Pp x Pp P p egg offspring P male / sperm sperm P PP P p p P 1/2 x 1/2 female / eggs 1/2 x 1/2 P PP Pp p Pp pp AP Biology 1/2 x 1/2 p p 1/2 x 1/2 = = = = 1/4 Pp 1/4 + 1/4 1/2 pp 1/4
  6. 6. 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 1/2 x 1/2 = 1/4  probability of Pp x Pp → pp 1/2 x 1/2 = 1/4 AP Biology P Pp p
  7. 7. Calculating probability in crosses Use rule of multiplication to predict crosses YyRr x YyRr x Yy Yy Rr yyrr x ?% 1/16 yy AP Biology rr 1/4 x 1/4 Rr
  8. 8. Apply the Rule of Multiplication AABbccDdEEFf x AaBbccDdeeFf AabbccDdEeFF Got it? Try this! AP Biology AA x Aa → Aa Bb x Bb → bb cc x cc → cc Dd x Dd → Dd EE x ee → Ee Ff x Ff → FF 1/2 1/4 1 1/2 1 1/4 1/64
  9. 9. Rule of addition  Chance that an event can occur 2 or more different ways  sum of the separate probabilities  probability of Bb x Bb → Bb sperm egg offspring B b Bb 1/2 x 1/2 = b B 1/2 x 1/2 = AP Biology 1/4 Bb 1/4 1/4 + 1/4 1/2
  10. 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 AP Biology
  11. 11. AP Biology
  12. 12. Any Questions?? AP Biology 2006-2007

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