Probability Genetics AP Biology 2006 2007 Genetics Probability

Probability & Genetics AP Biology 2006 -2007

Genetics & Probability § Mendel’s laws: segregation u independent assortment u reflect same laws of probability that apply to tossing coins or rolling dice AP Biology

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

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

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

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

DIHYBRID CROSS § A cross that involves two pairs of contrasting traits. AP Biology

DIHYBRID CROSS RY Ry r. Y ry RRYY RRYy Rr. YY Rr. Yy RRyy Rr. Yy Rryy Rr. YY Rr. Yy rr. YY rr. Yy Rryy rr. Yy rryy AP Biology

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

Apply the Rule of Multiplication AABbcc. Dd. EEFf x Aa. Bbcc. Ddee. Ff Aabbcc. Dd. Ee. FF Got it? Try this! AP Biology AA x Aa Bb x Bb bb cc x cc Dd x Dd EE x ee Ee Ff x Ff FF 1/2 1/4 1 1/2 1 1/4 1/64

Rule of addition § Chance that an event can occur 2 or more different ways u sum of the separate probabilities u probability of Bb x 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 1/2

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”? u or is there another factor influencing data? u § null hypothesis § degrees of freedom § statistical significance AP Biology

AP Biology

Any Questions? ? AP Biology 2006 -2007