homework 4
4.01 The French biologist Cuenot crossed wild, gray-colored mice with white (albino) mice. In the first generation, all were gray. He then crossed the F1 mice among themselves. From many litters, he obtained in the F2 generation 198 gray mice and 72 white mice.
4.01 The French biologist Cuenot crossed wild, gray-colored mice with white (albino) mice. In the first generation, all were gray. He then crossed the F1 mice among themselves. From many litters, he obtained in the F2 generation 198 gray mice and 72 white mice.
(a) Propose a hypothesis to explain these results. Diagram both generations (phenotype and genotype) based on your hypothesis.
(a) Propose a hypothesis to explain these results. Diagram both generations (phenotype and genotype) based on your hypothesis.
(b)Test your hypothesis using a chi-square test.
(b)Test your hypothesis using a chi-square test.
4.02 In peas, axillary flowers (A) is dominant to terminal flowers (a) and colored flowers (R) is dominant to white (r). A true-breeding plant with white, terminal flowers is crossed with a true-breeding plant having colored, axillary flowers. The F1 plants are then allowed to self-pollinate.
4.02 In peas, axillary flowers (A) is dominant to terminal flowers (a) and colored flowers (R) is dominant to white (r). A true-breeding plant with white, terminal flowers is crossed with a true-breeding plant having colored, axillary flowers. The F1 plants are then allowed to self-pollinate.
(a) Using the forked line method, list all possible F2 phenotypes and calculate the probability of each.
(a) Using the forked line method, list all possible F2 phenotypes and calculate the probability of each.
(b) The F2 generation consisted of 308 plants with axillary, colored flowers; 34 plants with terminal, white flowers; 118 plants with axillary, white flowers; and 132 plants with terminal, colored flowers. Using the chi-square test, determine if this outcome is consistent with the predicted ratios for this cross.
(b) The F2 generation consisted of 308 plants with axillary, colored flowers; 34 plants with terminal, white flowers; 118 plants with axillary, white flowers; and 132 plants with terminal, colored flowers. Using the chi-square test, determine if this outcome is consistent with the predicted ratios for this cross.
4.03 You are doing a cross with Drosophila using the following two traits. Curly wings is dominant over straight wings, and round eyes is dominant over elliptical eyes. You cross a female fly that is known to be heterozygous for both genes with a male that is heterozygous for the wing gene but has elliptical eyes. This cross produces 74 flies with curly wings and round eyes, 61 with curly wings and elliptical eyes, 24 with straight wings and round eyes, and 21 with straight wing and elliptical eyes. Calculate the expected phenotype ratios for this cross, then use the chi-square test to see if the observed data are consistent with the expected numbers.
4.03 You are doing a cross with Drosophila using the following two traits. Curly wings is dominant over straight wings, and round eyes is dominant over elliptical eyes. You cross a female fly that is known to be heterozygous for both genes with a male that is heterozygous for the wing gene but has elliptical eyes. This cross produces 74 flies with curly wings and round eyes, 61 with curly wings and elliptical eyes, 24 with straight wings and round eyes, and 21 with straight wing and elliptical eyes. Calculate the expected phenotype ratios for this cross, then use the chi-square test to see if the observed data are consistent with the expected numbers.
4.04 Calculate the probability of obtaining each of the following outcomes when flipping two coins simultaneously: (a) both heads, (b) both tails, and (c) one head and one tail. Now generate some actual data by flipping two coins 30 times are recording the number of each kind of outcome. Then use a chi-square test to see if your data are consistent with your predicted probabilities.
4.04 Calculate the probability of obtaining each of the following outcomes when flipping two coins simultaneously: (a) both heads, (b) both tails, and (c) one head and one tail. Now generate some actual data by flipping two coins 30 times are recording the number of each kind of outcome. Then use a chi-square test to see if your data are consistent with your predicted probabilities.
4.05 An ordinary 6-sided die is rolled repeatedly with the following outcome: 63 ones, 31 twos, 54 threes, 46 fours, 51 fives, and 55 sixes. Would you conclude from this data that it is a fair die? Give statistical support (chi-square test) for your conclusion.
4.05 An ordinary 6-sided die is rolled repeatedly with the following outcome: 63 ones, 31 twos, 54 threes, 46 fours, 51 fives, and 55 sixes. Would you conclude from this data that it is a fair die? Give statistical support (chi-square test) for your conclusion.
4.06 The pedigree shows the pattern of inheritance for a rare human disease. Filled symbols indicate individuals with the disease; open symbols indicate normal individuals.
4.06 The pedigree shows the pattern of inheritance for a rare human disease. Filled symbols indicate individuals with the disease; open symbols indicate normal individuals.
(a) What is the most probable mode of inheritance (dominant or recessive) for this trait?
(a) What is the most probable mode of inheritance (dominant or recessive) for this trait?
(b) What is the most convincing evidence you can give for your answer to (a)?
(b) What is the most convincing evidence you can give for your answer to (a)?
(c) What are the most probable genotypes of individuals II-I and II-2?
(c) What are the most probable genotypes of individuals II-I and II-2?
(d) If individuals II-6 and II-7 have another child, what is the probability that it will be normal?
(d) If individuals II-6 and II-7 have another child, what is the probability that it will be normal?
4.07 The following pedigree shows the pattern of inheritance for a rare human disease. Filled symbols indicate individuals with the disease: open symbols indicate normal individuals.
4.07 The following pedigree shows the pattern of inheritance for a rare human disease. Filled symbols indicate individuals with the disease: open symbols indicate normal individuals.
(a) What is the most probable mode of inheritance (dominant or recessive) for this trait? On what do you base your answer?
(a) What is the most probable mode of inheritance (dominant or recessive) for this trait? On what do you base your answer?
(b) What are the most probable genotypes of individuals I-1 and I-2?
(b) What are the most probable genotypes of individuals I-1 and I-2?
(c) What are the most probable genotypes of individuals II-9 and II-10?
(c) What are the most probable genotypes of individuals II-9 and II-10?
(d) If individuals II-1 and II-2 have another child, what is the probability that it will have the disease?
(d) If individuals II-1 and II-2 have another child, what is the probability that it will have the disease?
4.08 In the following hypothetical pedigree, there are two traits considered. One gene determines if a person is a vampire or not; the other gene determines if a person is a werewolf or not. The two genes sort independently. Study the diagram then answer the questions below. (HINT: Examine each trait separately when working out the genotypes.)
4.08 In the following hypothetical pedigree, there are two traits considered. One gene determines if a person is a vampire or not; the other gene determines if a person is a werewolf or not. The two genes sort independently. Study the diagram then answer the questions below. (HINT: Examine each trait separately when working out the genotypes.)
(a) Is being a vampire due to a dominant or recessive allele? How can you tell?
(a) Is being a vampire due to a dominant or recessive allele? How can you tell?
(b) Is being a werewolf due to a dominant or recessive allele? How can you tell?
(b) Is being a werewolf due to a dominant or recessive allele? How can you tell?
(c) Give the most likely genotypes for individuals I-2, II-3, and II-6. Use D and d for the alleles of the vampire gene and R and rfor the alleles of the werewolf gene.
(c) Give the most likely genotypes for individuals I-2, II-3, and II-6. Use D and d for the alleles of the vampire gene and R and rfor the alleles of the werewolf gene.