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AP Lab #7: Genetics of Organisms Pre-Lab 2 Problems Read each question carefully. Use the 2 statistical test to determine if the various hypotheses regarding patterns of inheritance are supported. On a separate sheet of paper, show all work for each question and put a box around your answer. 1. You hypothesize that you have one autosomal dominant trait. You crossed the following true breeding parents: wild type female and mutant male. In the F2 generation you observe the following phenotypes: 35 dominant females, 35 dominant males, 20 recessive males, and ten recessive females. Show your chi-square calculations, and is your hypothesis supported? 2. You are studying hair length in wild yaks and perform the standard genetic crosses. You suspect that the short hair allele is sex-linked recessive. In the following observations, assume both parents are true breeding. Test your hypothesis with a Chi-square test. Show all your calculations for the Chi-Square. P: short haired male X long haired female F1: 145 long haired males and 155 short haired females (F2 is a cross of F1 male and female) F2: 73 long haired females; 77 short haired females; 72 long haired males, 78 short haired males. 3. You are analyzing a dihybrid cross where both mutant traits are autosomal recessive in a Scooby Doo species. You set up the cross with each true breeding parent exhibiting one wild type trait. You observe A = brown, a = gray and M = munchies, m = no munchies. In the F2 generation you observe 152 brown munchie having scoobys, 48 brown no munchie having scoobys, 42 grey munchie having scoobys and 12 grey no munchie having scoobys. Test your hypothesis with a Chi-square test. Show all your calculations for the Chi-Square. 4. Suppose that a cross between two pea plants yields a population of 880 plants, 639 with green seeds and 241 with yellow seeds. You are asked to propose the genotypes of the parents. Your hypothesis is that the allele for green is dominant to the allele for yellow and that the parent plants were both heterozygous for this trait. If your hypothesis is true, then the predicted ratio of offspring from this cross would be 3:1 (based on Mendel's laws) as predicted from the results of the Punnett square. Test your hypothesis with a Chi-square test. Show all your calculations for the Chi-Square. 5. In sweet peas, purple flowers (A) are dominant to white (a). However, a second gene codes for an enzyme involved in pigment production; at least one copy of the dominant allele for this gene (B) must be present for purple flowers to be possible. In other words, bb plants have white flowers even if they are AA or Aa. Two purple-flowered plants that are AaBb are crossed: AaBb x AaBb. Their offspring are used to establish a population. After a number of generations for that population, you randomly sample 100 plants and count 58 purple-flowered plants and 42 white-flowered plants. Calculate chi-square for distribution of flower color. What are your degrees of freedom? What percentage of the time would you expect this deviation due to chance? 6. In Drosophila, eye color is an X-linked trait, and females are XX while males are XY. The alleles for eye color are: XR = red eyes (dominant) Xr = white eyes (recessive) Y = no allele (Y chromosome) Your oh-so kind biology teacher gives you a male fly and a female fly as gifts, and you decide to start a colony: Parents XRXr x Xr Y You allow the offspring of these parents to interbreed, and continue interbreeding for several generations. Soon your population reaches over 1000 flies. You take a random sample of 100 flies and observe: 30 red-eyed females 28 red-eyed males 22 white-eyed females 20 white-eyed males Do the following: Calculate chi-square value for your results (combined calculation for both eye color and sex). What are your degrees of freedom? What percentage of the time would you expect this deviation due to chance?