Genetics Chi Square Answer Key - AP Biology, Exercises of Biology

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AP Biology Chi Square Practice Problems Chi-square is a statistical tool that helps us to decide if the observed ratio is close enough to the expected ratio to be acceptable. Chi-square analysis can be used in any area, not just genetics. Whenever you have to determine if an expected ratio fits an observed ratio, you can use the Chi-square. X2 = Z (O-E)? E Chi Square Significance Table Degrees of 5% Probability Freedom (n) Value (P) 3.84 5.99 81 ji ' 9.49 y 1. In peas, yellow seeds (A) are dominant over green (a) seeds. In a cross between two plants both heterozygous for seed color, the following was observed: Yellow= 4400 Green= 1624 Does the data fit the predicted phenotypic ratio? ° 7 Nx expecicd phenctypic raho ello * ° c F iF A= green Aa Aa y 3: | ; aA o:A AIA yellan: green A A oben, Phenotype | Obseved (O) | Expected (E) O-E (Q-E)? Yeilow 4+0c CRAG) 4518 -118 Green 1624 CRATE 1506 ig Totals 6024 6024 N-2-1=1 Neo, data docs not Fit pitdicted Phenctpe as P= 3.84 12.32 > 3.64 2. In peas, smooth seeds (R) are dominant over wrinkled (r) seeds. In the P generation, a plant homozygous for smooth seeds is crossed with a plant with wrinkled seeds. The resulting F, plants are crossed. The seeds of the observed F. generation were: Smooth = 5474 Wrinkled = 1850 Does the data fit the predicted phenotypic ratio? ¢ Rr x Er | e jr expected Phenshypic ravic = smooth P: Pexrt Fo fa r= wrinkled ib 9 oo F reer BN Fy: &@r © E Fr c irle | amosth > wyinkled Phenotype | Obseved (O) | Expected (E) 0-E (O-E)2 (Q-E)2 E 5oetN 541+ THAT) 5493 =19 36) 0.01 = By winked 1856 Wee24C5), iso i9 361 el. Totals 1324 1324 0.27 N= 2-1=\ Yes the data fits the predicted phenompe P= 3.84 6.24 = 384