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Background Information: There are two primary steps to alcohol metabolism. First, alcohol is converted to acetaldehyde via the enzyme alcohol dehydrogenase (ADH). Second, acetaldehyde is converted to acetate via the enzyme aldehyde dehydrogenase (ALDH). The ADH gene, located on chromosome 4, codes for the ADH enzyme. The ALDH gene, located on chromosome 12, codes for the ALDH enzyme. Acetaldehyde is a toxic substance whose accumulation leads to an “alcohol flush reaction,” which includes facial flushing, nausea, and rapid heartbeat. The ALDH gene has two primary alleles. The dominant D allele results in production of nonfunctional ALDH enzyme. This results in a build-up of acetaldehyde and a flush reaction when an individual consumes alcohol. The recessive d allele results in production of a functional ALDH enzyme and lack of a flush reaction. First, we are interested in the presence or absence of the flush reaction phenotype. 1. Jasmine and her mother both get a flush reaction when they drink alcohol. Jasmine’s father does not. Jasmine’s husband, Jake, does not get a flush reaction, but his mother and father both do. a. Draw a pedigree of Jasmine, Jake, and their parents. Label each individual with his/her genotype. b. What genotypic ratio is expected among Jasmine and Jake’s kids? Show your work with a Punnett square. c. What proportion of Jasmine and Jake’s kids are expected to exhibit the flush reaction? Explain. 2. The ADH gene also has two primary alleles. One allele, A, codes for a form of the ADH enzyme that catalyzes the conversion of alcohol into acetaldehyde approximately 80 times faster than the form encoded by the a allele. AA individuals exhibit fast conversion, Aa individuals exhibit medium conversion, and aa individuals exhibit slow conversion of alcohol into acetaldehyde. In this question, we are interested in “conversion rate” as a trait. The possible phenotypes are fast, medium, and slow. a. Does the ADH gene exhibit dominance, incomplete dominance, or codominance with respect to the alcohol conversion rate? Explain your answer. b. Jasmine and Jake both exhibit a medium rate of conversion of alcohol into acetaldehyde. What proportion of their kids are expected to exhibit fast conversion, medium conversion, or slow conversion of alcohol? Show your work with a Punnett square and explain. 3. Now consider both the ADH and the ALDH genes at the same time. a. Write out Jasmine’s genotype, including both the ADH and the ALDH genes (e.g, AADd, or whatever the correct genotype is). Do the same for Jake. b. Draw a single Punnett square showing the expected genotypic ratio of Jasmine and Jake’s kids, considering both genes together. c. Write out the expected phenotypic ratio of Jasmine’s and Jake’s kids, considering both traits together. For example, how many will have a flush reaction and fast rate of conversion? How many will have no flush reaction and a medium rate of conversion? Etc. 4. The figures below show possible arrangements of chromosomes during meiosis in the germ cells of Becky, who is a double heterozygote for the ADH and ALDH genes (AaDd). Becky’s father was AADD and her mother was aadd. a. Using Figure 1 below, draw how the alleles for these genes would be arranged on the chromosomes, given that they segregate independently. Note that the figure contains only 2 of the 23 kinds of chromosomes due to space constraints. b. Using Figure 2 below, draw how the alleles for these genes would be arranged on the chromosomes if they were tightly linked (i.e., assume there has been no crossing over between them). c. Becky married Juan, who also had one AADD and one aadd parent. Draw two Punnett squares representing the expected proportions of genotypes among Becky and Juan’s children. Use the first square to represent what would happen with independent assortment and the second square to represent what would happen if the genes are tightly linked (i.e., there is no crossing over between them). d. What are the expected proportions of offspring phenotypes for each case? e. How does independent assortment affect the genetic and phenotypic diversity of the offspring, compared to dependent assortment? Explain. 5. Both the ADH and ALDH genes contribute to an individual’s probability of developing alcohol dependence, a disease that is relatively common and often devastating. Inability to convert acetaldehyde to acetate results in a flush reaction that makes alcohol consumption extremely unpleasant. Meanwhile, fast conversion of alcohol to acetaldehyde quickly removes the pleasurable effects of alcohol. People with a flush reaction essentially never develop alcohol dependence, no matter how fast or slow they convert alcohol into acetaldehyde. Consuming alcohol is just too unpleasant. Among those without a flush reaction, people with the AA genotype (fast converters) are least likely to develop alcohol dependence. People with the Aa genotype (medium converters) are roughly 5 times as likely and people with the aa genotype (slow converters) are roughly 10 times as likely to develop alcohol dependence as people with the AA genotype. Many other factors also influence whether or not an individual develops alcohol dependence, including that person’s culture, education, religion, health care, family environment, and social support network. a. Given the information presented in this problem set so far, which extensions to Mendelian genetics (listed below) are involved in the trait of alcohol dependence? Give a brief explanation for every extension so that I can evaluate your reasoning for choosing it or not. 1. Linkage 2. Incomplete dominance 3. Codominance 4. More than 2 alleles per gene 5. Polygenic Inheritance 6. Epistasis 7. Pleiotropy 8. Environmental Influence 9. Sex linkage b. So far, I have given you only part of the story of alcohol dependence; the whole picture is more complex. There are actually many different ADH genes located very close together on chromosome 4, many different alleles for both the ADH and ALDH genes, and many additional genes involved in this trait, including at least one on the X chromosome. Many of these genes influence other traits, such as anxiety or ability to detoxify other substances, in addition to the tendency to develop alcohol dependence. Researchers are actively discovering more about the genetics underlying this trait each year. Given this information, which additional extensions to Mendelian genetics apply to alcohol dependence? Give a brief explanation for every extension that you did not choose in part a above so that I can evaluate your reasoning for choosing it or not. 6. A mother and her child both have blood type A. a. What are the possible genotypes of the father? Remember to use the correct symbols for the alleles (e.g., IB ). b. The mother has a second child (with the same father) and that child has a blood type of O. Now, considering both children, what are the possible genotypes of the father? c. Considering both children, what is the genotype of the mother? 5. Both the ADH and ALDH genes contribute to an individual’s probability of developing alcohol dependence, a disease that is relatively common and often devastating. Inability to convert acetaldehyde to acetate results in a flush reaction that makes alcohol consumption extremely unpleasant. Meanwhile, fast conversion of alcohol to acetaldehyde quickly removes the pleasurable effects of alcohol. People with a flush reaction essentially never develop alcohol dependence, no matter how fast or slow they convert alcohol into acetaldehyde. Consuming alcohol is just too unpleasant. Among those without a flush reaction, people with the AA genotype (fast converters) are least likely to develop alcohol dependence. People with the Aa genotype (medium converters) are roughly 5 times as likely and people with the aa genotype (slow converters) are roughly 10 times as likely to develop alcohol dependence as people with the AA genotype. Many other factors also influence whether or not an individual develops alcohol dependence, including that person’s culture, education, religion, health care, family environment, and social support network. a. Given the information presented in this problem set so far, which extensions to Mendelian genetics (listed below) are involved in the trait of alcohol dependence? Give a brief explanation for every extension so that I can evaluate your reasoning for choosing it or not. 1. Linkage 2. Incomplete dominance 3. Codominance 4. More than 2 alleles per gene 5. Polygenic Inheritance 6. Epistasis 7. Pleiotropy 8. Environmental Influence 9. Sex linkage b. So far, I have given you only part of the story of alcohol dependence; the whole picture is more complex. There are actually many different ADH genes located very close together on chromosome 4, many different alleles for both the ADH and ALDH genes, and many additional genes involved in this trait, including at least one on the X chromosome. Many of these genes influence other traits, such as anxiety or ability to detoxify other substances, in addition to the tendency to develop alcohol dependence. Researchers are actively discovering more about the genetics underlying this trait each year. Given this information, which additional extensions to Mendelian genetics apply to alcohol dependence? Give a brief explanation for every extension that you did not choose in part a above so that I can evaluate your reasoning for choosing it or not. 6. A mother and her child both have blood type A. a. What are the possible genotypes of the father? Remember to use the correct symbols for the alleles (e.g., IB ). b. The mother has a second child (with the same father) and that child has a blood type of O. Now, considering both children, what are the possible genotypes of the father? c. Considering both children, what is the genotype of the mother?