 1. Write the equation for chi-squared and define each of the terms.  2. What p-value do we use in AP Biology?  3. In a dihybrid cross, what fractions do we expect if the parents are both heterozygous? 2/2 Daily Catalyst Pg. 76 Chi-Squared

 Unit #7 test Genetics  Wednesday, Feb. 3 rd  Study guide due test day  Blood types lab tomorrow  Tutoring available!  Unit #8 Energy  Mini-test Thursday, Feb.12 th  Review packet over Mardi Gras 2/2 Class Business Pg. 76 Chi-Squared

 Daily Catalyst  Class Business  Review pedigrees  Chi-squared problems  Practice 2/2 Agenda Pg. 76 Chi-Squared

 You are looking at two traits, kernel color and texture. To obtain the variety we see below, the parents (p gen) must have been heterozygous for both traits. Purple and smooth are dominant traits and yellow and wrinkled are recessive traits.  Due to the phenotypic ratio we know, what do we expect?  9/16 Purple and smooth  3/16 Purple and wrinkled  3/16 Yellow and smooth  1/16 Yellow and wrinkled Chi-Squared

 When you count the kernels on the corn cob, you see the following data:  Is this that we expect? Chi-Squared Kernels# Counted Purple and smooth 12 Purple and wrinkled 9 Yellow and smooth 7 Yellow and wrinkled 6 Total34

kernelsRatioDecimalWorkExpectedObserve Purple and smooth 9/ X Purple and wrinkled 3/ X Yellow and smooth 3/ X Yellow and wrinkled 1/ X =1.00=34 Chi-Squared

 Answer

 1. Problem: A large ear of corn has a total of 433 grains, including 271 Purple & starchy, 73 Purple & sweet, 63 Yellow & starchy, and 26 Yellow & sweet.  Your Tentative Hypothesis: This ear of corn was produced by a dihybrid cross (PpSs x PpSs) involving two pairs of heterozygous genes resulting in a theoretical (expected) ratio of 9:3:3:1.  Objective: Test your hypothesis using chi square and probability values. Problem #1

 Expected  Purple and Smooth 9/16 of 433 = Purple and Wrinkled 3/16 of 433 = 81.2 Yellow and Smooth 3/16 of 433 = 81.2 Yellow and Wrinkled 1/16 of 433 = 27.1

 2. Problem: In a certain reptile, eyes can be either black or yellow. Two black eyed lizards are crossed, and the result is 72 black eyed lizards, and 28 yellow- eyed lizards.  Your Tentative Hypothesis: The black eyed parents were Bb x Bb.  Objective: Test your hypothesis using chi square analysis.  Expected  If you do a punnet square of Bb x Bb, you get an expected percentage of 25% and 75% or 1/4 and 3/4  Since the total number of lizards is 100, the observed is already in the correct ration  Expected Observed  Black Eyes = Yellow Eyes =  =.48  Good FIT Problem #2

 3. Problem: A sample of mice (all from the same parents) shows  58 Black hair, black eyes 16 Black hair, red eyes 19 White hair, black eyes 7 White hair, red eyes  Your tentative hypothesis: (what are the parents?)  Looks like a 9/3/3/1 ratio, meaning the parents are HhEe x HhEe  Total number of offspring = 100  Expected  9/16 of 100 = /16 of 100 = /16 of 100 = /16 of 100 = 6.25  =.54 = GOOD FIT Problem #3

2/2 HW  1. In a certain species of flowering plant, the red allele R is dominant to the white allele, r. A student carried out a cross between a red flowered plant and a white flowered plant. When planted, the 158 seeds that were produced from the cross matured into 92 plants with red flowers and 66 plants with white flowers. Calculate the chi squared value for the null hypothesis that the red flowered parent was a hybrid for the flower color gene. Give your answer to the nearest tenth.

2/2 HW  1. A genetics engineer was attempting to cross a tiger and a cheetah. She predicted a phenotypic outcome of the traits she was observing to be in the following ratio: 4 stripes only, 3 spots only, 9 both stripes and spots. When the cross was performed and she counted the individuals she found 50 with stripes only, 41 with spots only and 85 with both. According to the Chi-square test, did she get the predicted outcome?

 Define nondisjunction  Provide an example  What is the impact of nondisjunction? 2/2 HW