Unformatted text preview: Part I. Terms: (26 points) 1. Explain how the terms heterozygous and homozygous are related to homologous chromosomes. (4 points) 2a. Although there are many types of genetic disorders, each involves changes to the cells DNA. Describe how each of the following types of genetic disorders impacts the cells DNA or chromosomes. Include in your answer which of these types of disorders involves nuclear DNA and which impacts mitochondrial DNA. (6 points) single gene disorder chromosomal disorder mt DNA disorder (not covered in lecture, a little research is needed). 2b. Give a specific example of a single-gene disorder and of a chromosomal disorder. Give a short description of each of the disorders selected. Your examples may not be one of the disorders discussed in lecture. (4 points) 2c. Which of these three disorders listed in 2a can be detected by examining a karyotype? Briefly support your answer. (2 points) Related Link Many of the answers to question 2 can be found at this link Cri du Chat Syndrome - this is the disorder I mentioned in lecture 3a. Describe three ways "X"-linked traits and autosomal traits differ from each other. (6 points) 3b. Explain why X-linked recessive disorders are more common in males than in females. (2 points) 3c. Describe a genetic disorder not covered in lecture that is X-linked. Reference where you found this information. (4 points) Related Link: I found this link while looking for more information on muscular dystrophy. It does a nice job explaining the different types of inheritance. Part II. Human Genetics Problems (79 points) A-C: AUTOSOMAL DISORDERS A. Autosomal Recessive Disorder: Cystic Fibrosis Background Information: Cystic Fibrosis (CF) is one of the most common genetic disorders among people of European descent. It occurs in 1 out of every 3,000 births and one in every 31 Americans is a carrier for the disorder. The allele for CF is recessive to being healthy. Cystic Fibrosis Links Cystic Fibrosis - Profile Molecular basis for Cystic Fibrosis Human Genome Project and Cystic Fibrosis A1. Discuss in a fair amount of detail the biological cause of cystic fibrosis. A complete answer will include information on how the DNA is mutated, the protein that is made incorrectly in CF patients, the consequences of this defect in the protein, and the role of the ER/Golgi. (5 points) A2. Explain why carriers of CF, although they have an allele for the defective protein, are healthy and symptom free. Your answer should clearly address the relationship between the individual's DNA and the membrane proteins they make. (2 points) A3. One of my former students has a beautiful daughter with CF, Sara Elizabeth. Both the student and the child's father are healthy. Explain how these two healthy parents could have a child with CF. Include in your answer the genotype of each parent and of the child. (3 points) Please the following letter code: H - healthy h = cystic fibrosis A4. If the couple in A3 were to have a second child, what is the risk that their second child would have CF? Support your answer. Is the sex of the baby related to the risk of CF? Why or why not? (4 points) A5. With new treatments individuals affected with CF are living longer. Thus, marriage and family are a possibility. Imagine Sara Elizabeth is grown-up and preparing to marry a healthy man. What would you tell them/her about their risk for having children with CF? Please be sure to consider all possibilities. For full credit, support your answer(s) with the genotypes of all involved. (You may want to consider the best-case and worst-case scenario.) (4 points) B. Autosomal Dominant Disorder: Marfan Syndrome Background Information: Marfan Syndrome is commonly inherited as an autosomal dominant disorder. (Although there appear to be forms of Marfan that are not inherited in this manner, you will assume it is an autosomal dominant disorder when answering this question.) Marfan syndrome is a genetic disorder that affects the strength of connective tissue. A serious and common consequence of this is a weak spot on the aorta. (The aorta is the major blood vessel leaving the heart with oxygenated blood.) For some reason most individuals with Marfan's are unusually tall and have long arms, fingers, and toes. (Many believe Abraham Lincoln had Marfan syndrome.) One of my favorite volleyball players died from Marfan syndrome in 1986. At the time of her death Flo Hyman was one of the best female volleyball players in the world. At 6'5" tall, she dominated the court and led the U.S. women's volleyball team to a silver medal at the 1984 Olympics. She died playing volleyball in Japan when her aorta burst during a game. Upon autopsy (her family did not believe she died of heart failure as diagnosed by the team physician) it was discovered the she had Marfan syndrome. Marfan Syndrome Related Links Marfan Syndrome - genetics and symptoms NIH Marfan Link - good information on the genetics Marfan Research Foundation Health Alert - Marfan's Syndrome B1. Given the genetic aspect of Marafan's Flo's family was screened. (The following concerning Flos' family is not true, but made-up for this question.) Her father and sister were diagnosed with Marfans while her mother and a brother were given a clean bill of health. Create a pedigree (family tree) for Flo Hyman's family -- to include: Flo, her parents, and her two siblings. Shade in the circles/boxes of individuals with Marfan syndrome. In addition, give as much information as possible about the genotype for each member of the family. Use the following letter key: M = Marfan syndrome, m = healthy. (6 points) B2. Discuss the genetic basis for Marfan Syndrome. Include in your answer information on the gene associated with Marfan syndrome and the protein affected. Some detail is needed for full credit. (4 points) B3 Occasionally two healthy parents with no family history of Marfan Syndrome have a child who is diagnosed with the condition. Explain why it would be unusual/unexpected for two healthy parents to have a child with a dominant disorder such as Marfans. (2 points) C. Co-Dominance - Blood Type Related Links: Blood Type Tutorial C1. Explain how a person could have type O blood if neither of their parents has type O blood. Give an example of parental genotypes that support your answer. (4 points) C2. Explain why an individual with type O blood is a universal blood donor, but can receive blood only type O blood. Fully support your answer. (4 points) C3. What component(s) of the plasma membrane plays a role in determining an individual's blood type? Be specific and briefly support your answer. Base some aspect of your answer on the information presented in Chapter 5. (3 points) C4. Although blood types can never be used to prove someone is the father of a particular child, they can demonstrate that someone could not be the father. In 1940 there was a famous paternity case involving Charlie Chaplin. A woman named Charlie as the father of her baby. Charlie denied the accusation and the case went to court. At the time Charlie Chaplin was judged to be the baby's father. At that time many states did not allow blood test results as evidence in cases of disputed paternity. You may/must use the blood types of the individuals to guide your answer. The baby's blood type was B, the mother's A, and Charlie Chaplin's O. (10 points) a) Based on the information in this question, give the possible genotype(s) of the woman, Charlie, the baby, and the baby's father if it's not Charlie. In some cases only one genotype is possible and in others multiple genotypes are possible. Be sure to fully think through the possible genotypes! b) Based on these genotypes, could Charlie be the babys father? Explain your answer. D-F: SEX-LINKED DISORDERS please pay attention to the 2 reminders! REMINDER #1: YOU MUST INCLUDE X and Y IN YOUR GENOTYPES WHEN ANALYZING X-LINKED TRAITS! (See page 176 of the text or the lecture for examples of how to write these genotypes. Do not make up your own format for showing these genotypes!) REMINDER #2: X and Y are NOT included in the genotypes when analyzing disorders that are not sex-linked. D. X-Linked Recessive: Duchenne Muscular Dystrophy Background Information: Duchenne muscular dystrophy (MD) is a relatively frequent genetically determined neuromuscular disease of childhood, with an incidence of 1 in every 3,500 births. The allele for muscular dystrophy is X-linked and recessive. In a typical case symptoms develop around age 3, when a peculiar gait and difficulty in getting up indicate a neuromuscular problem. In a third of the patient there is also mental retardation. The ability to walk is usually lost between ages 9 and 12. By age 20 there respiratory and heart problems often develop. Spinal deformities may also occur, contributing to respiratory and heart problems. Few Duchenne patients live in to their thirties. Related links: MD - site aimed at teens and their parents Muscular Dystrophy Association My friend Thomas has Duchenne muscular dystrophy. Tom graduated from high school three years ago after completing the full academic-track curriculum. He's a math and chemistry whiz-kid. Tom is confined to a wheel chair and has essentially no ability to move muscles below his neck. He cannot feed himself, turn the pages of a book, or do much else. Recently even breathing has become difficult. Tom loves the Red Sox, Harry Potter, and soccer. With research children like Tom will someday have a chance to live a full life. For now, the World cup, the Red Sox, and the anticipation of the next Harry Potter movie bring joy to what is likely to be short life. The questions concerning muscular dystrophy follow in the next paragraph. I read a case study (true story) of a family who had a son with MD. When the son was first diagnosed with MD the doctor told the mother that "half on any sons she would have might develop MD". He also told her of the likely consequences of the disease as her son grew. She understood him to say that there was no medical treatment available (there is some that would have improved her sons quality of life). She went on the have two more sons, self-diagnosed them to have MD, and did not obtain medical treatment for any of the sons. She has a healthy daughter. Their story came to light soon before her youngest son died. More detailed information on the family follows. Both the woman and her husband are healthy. D1. Create a pedigree for the family in the case study. Shade in the circles/boxes of the individuals with MD. In addition, give as much information as possible about each family member's genotype. If more than one option is possible please show both. Don't forget this is an X-linked disorder. Letter Key: H = healthy h = muscular dystrophy (6 points) D2. What did the physician mean when he/she told the woman that half of any sons she had might develop MD? Was the woman correct in interpreting this as; if she had 4 boys, 2 would be healthy and 2 would have MD? (4 points) D3. Discuss the biological cause of Duchenne muscular dystrophy. Your answer should include the relationship between the DNA, the proteins made, and the symptoms. (4 points) E. X-Linked Recessive: Coloboma Iridis ..NO additional research on the disorder is needed to answer this question. Base your answer on the information in the question only. Background Information: Coloboma iridis is a genetic disorder that results in a fissure in the iris of the eye. In many cases trait is X-linked and recessive to "normal" (no eye fissure) eyes. E1. (This one is not a real story. It comes from a genetics textbook) Upon the birth of their first child the husband accuses his wife of being unfaithful. His grounds for this claim are as follows. Both the husband and his wife have normal eyes, yet their daughter has coloboma iridis. Is the husband's claim that he is not the baby's father grounded? Fully support your answer by giving the genotype of the baby, mother, and the husband. In addition, give the genotype of the baby's father if you believe it is not the husband. (6 points) Letter Key: I = normal eyes i = coloboma iridis E2: Fully explain how/if your answer would have been different if the baby had been a son with an eye fissure. (4 points) F3: Y-Linked Trait: Hairy Ears! The allele for hairy ears is located on the Y chromosome. No genetic information for this trait is located on the X chromosome. A man with hairy ears is married to a woman without hair in her ears. They have 2 daughters and two sons. Would you expect any of their children to have hairy ears? (Be as specific as possible.) Explain your answer. (4 points) ...
View Full Document
- Spring '08