Part I: Concern About Sickle Cell and NCAA Testing

Transcription

1 Part I: Concern About Sickle Cell and NCAA Testing You are encouraged to work with other students, but each person must submit the assignment individually. There will be no group assessment on this assignment. In the last decade, more than 20 college football players have died while training. Almost 40% are known to have had sickle cell trait, a condition in which a person has one atypical hemoglobin gene (HbS), in addition to the typical version (HbA). Different gene versions are known as alleles. Hemoglobin is the protein in red blood cells that carries oxygen throughout the body. Under some conditions, hemoglobin produced from the mutated form of the gene will crystallize, converting the disk-shaped red blood cells into a sickle shape. These deformed cells can clog blood vessels, disrupting blood flow in the body, potentially leading to more serious health effects. If an individual has two sickle cell alleles (HbS/HbS), they are said to have sickle cell disease, which can present some health problems. People with sickle cell disease often have symptoms such as anemia (a low number of red blood cells) and periodic episodes of pain cause by clogged blood vessels. Blocked blood flow can deprive organs of oxygen, causing damage. Occasionally, high blood pressure in lung blood vessels can lead to heart failure. Sickle cell trait, in which individuals have one normal allele and one mutated allele (HbS/HbA) is relatively common, occurring in approximately 8% of African-Americans and approximately 1% of Caucasian-Americans. Because individuals with sickle cell trait have one normal allele, in addition to the one mutated copy, they produce normal hemoglobin in addition to the sickling form. As a result, most live perfectly normal lives, showing few symptoms; in fact, many don't even know that they carry the trait. However, sickling becomes more common at low oxygen levels such as those created by strenuous exercise. A string of deaths in college football players from 2000 to 2009 led the National Collegiate Athletic Association (NCAA) to institute a new sickle cell policy for all incoming Division I student-athletes. Starting the academic year, studentathletes must be tested for sickle cell trait, show proof of a prior test or sign a waiver releasing an institution from liability if they decline to be tested (Brutlag Hosick 2010). Eric and Gina will be attending college next year on athletic scholarships. The two have been dating for the last year and have just heard about the new sickle cell policy instituted by the NCAA. Eric is concerned about the policy because he thinks that it could unfairly prevent him from playing or, even worse, result in the loss of his scholarship. He knows his father has the sickle cell trait. Most importantly, he thinks that the policy results in racially biased consequences because students of African, Mediterranean, and South American decent are more likely to carry the trait. Gina shares his concerns, but thinks that the policy will save lives. WSBCTC 1

2 Works Cited (1) Brutlag Hosick, M Protocol decided for sickle cell testing. NCAA News 13 April What is the molecular basis of sickle cell disease? 2. What is the mutation that occurs and how does this result in sickle-shaped red blood cells? WSBCTC 2

3 3. If Eric's mother does not have the sickle cell trait, what is the probability that Eric has the trait? 4. If Eric's mother does have the sickle cell trait, what is the probability that Eric has the trait? 5. Why are certain groups more likely to carry the sickle cell trait? WSBCTC 3

4 6. Sickle cell disease was once very likely to lead to mortality prior to reproductive age. If this is the case, how has sickle cell trait remained so common? Shouldn't natural selection have reduce its frequency in the human population? 7. Should the NCAA require testing of student-athletes? Why or why not? WSBCTC 4

5 Five years later, Eric and Gina graduated from college and decided to get married. Both attended college on athletic scholarships and did well both academically and athletically. Gina was tested for the sickle cell trait and discovered that she had it. She made only minor adjustments to her training and never had any noticeable symptoms of the sickle cell trait. Eric decided not to be tested, signing the waiver that allowed him to compete. Eric made no adjustments to his training because he was already cautious. Eric knew his father had the sickle cell trait, so he assumed there was a chance that he had it as well. The couple is considering having children. However, knowing that Gina has the sickle cell trait and that Eric's father has the sickle cell trait, they decided to discuss sickle cell with a doctor before making their decision. If you were Eric's and Gina's doctor, what would you tell them? 8. What are the three possible genotypes of their children? 9. What are the possible phenotypes? WSBCTC 5

6 10. Is sickle cell dominant, recessive, or codominant? Justify your answer. 11. If Eric does have the sickle cell trait, what is the probability that their first child would have the sickle cell trait? 12. If Eric has the sickle cell trait, what is the probability that their second child would have the sickle cell trait? 13. If Eric does not have the sickle cell trait, what is the probability that their first child would have sickle cell trait? WSBCTC 6

7 14. If Eric has the sickle cell trait, what is the probability that their first child would be unaffected by sickle cell? 15. If Eric has the sickle cell trait, what is the probability that their first child would have sickle cell disease? 16. If Eric and Gina decide to have 2 children, and he has the sickle cell trait, what is the probability that both of their children would have sickle cell disease? 17. If Eric and Gina decide to have 2 children, and he has the sickle cell trait, what is the probability that both of their children would have sickle cell trait? WSBCTC 7

8 18. If Eric and Gina decide to have 2 children, and he has the sickle cell trait, what is the probability that at least one of their children would have sickle cell disease? 19. If you were Gina's and Eric's doctor, what would you tell them in order for them to make an informed decision regarding whether or not to have children? WSBCTC 8