Tuesday, February 22, 2011

In Sickness and Health!


In Biology we've been working on the sickness and health activity where we work at being genetic counselors. The following questions are each of the stages that i passed to finish the activity. Check out the website here.


Questions

  1. Do autosomal dominant disorders skip generations? No because they need to have a female carrier. 
  2. Could Greg or his mother be carriers of the gene that causes myotonic dystrophy? His mother could be a carrier but Greg could not because he is male.
  3. Is there a possibility that Greg’s aunt or uncle is homozygous for the myotonic dystrophy (MD) gene? Yes.
  4. Symptoms of myotonic dystrophy sometimes don’t show up until after age fifty. What is the possibility that Greg’s cousin has inherited the MD gene? There is a 50/50 chance that Greg's cousin inherited MD. 
  5. What is the possibility that Greg and Olga’s children could inherit the MD gene? There isn't a chance because Greg can not be a carrier without having symptoms of the disease. 

Questions

  1. What are the hallmarks of an autosomal recessive trait? There are five hallmarks of autosomal recessive inheritance:
    1. Males and females are equally likely to be affected.
    2. On average, the recurrence risk to the unborn sibling of an affected individual is 1/4.
    3. The trait is characteristically found in siblings, not parents of affected or the offspring of affected.
    4. Parents of affected children may be related. The rarer the trait in the general population, the more likely a consanguineous mating is involved.
    5. The trait may appear as an isolated (sporadic) event in small sibships
  2. What does consanguineous mean? Why is this concept especially important when discussing recessive genetic disorders? It means people coming from the same ancestor, this is important because if two people are related then it is more likely they will receive the disease.
  3. What is it about the inheritance pattern of factor VIII deficiency seen in Greg and Olga’s pedigree that point toward it not being an autosomal recessive trait? The pattern seems to stay mostly in boys, making women carriers. 

Questions

  1. What are the characteristics of X-linked recessive inheritance? The characteristics are that they are only passed on to boys and the disease does not affect women.
  2. Why does a son never inherit his father’s defective X chromosome? The mother has to pass on the gene to her son.
  3. What is required for a woman to display a sex-linked recessive trait? She would have had to inherit it from her mother.
  4. Return to the pedigree drawn earlier for Greg and Olga; mark those persons who are carriers of the factor VIII deficiency gene. Link to Picture
  5. What is the chance that Olga carries the gene for factor VIII deficiency? Calculate the probability that she will pass it to her offspring. Will male children be affected in a different way than female children? There is a 50% chance that she will pass the VII deficiency to her children.
  6. What is the chance that Greg carries the factor VIII gene? Can he pass the gene on to his sons? His daughters? How will each be affected? There is a 25% chance that he will the gene onto his children. He wouldn't be able to pass the genes onto his children.

Questions

  1. What is the second equation? 1 of 3,000
  2. The incidence of cystic fibrosis in Hispanic Americans is 1/4500 while in African Americans cystic fibrosis is seen in 1 of every 15,000 births. What is the carrier frequency for each of these populations? 1 in every 3 women.
  3. What is the probability of two Hispanic Americans having a child with cystic fibrosis, given that there is no history of the disease in either’s family? Zero percent.
  4. Carol is an African American woman who does not suffer from CF. Both of her parents are healthy but her brother has cystic fibrosis. Carol is planning a family with her husband Marcus, who is also African American but who has no history of CF in his family. What is the probability of their having a child with CF? 50%

Questions

  1. What are some of the risks and benefits of genetic testing as it relates to legal (not medical) issues? Risks of genetic testing are that the child could miss out on job opportunities or be prejudiced. Benefits are that they can catch the disease early on and help. 
  2. Do you think an unintended consequence of genetic testing could be that people would be less liable to seek medical care out of fear that they could later be denied life or health insurance? What laws should be used to govern the use of genetic data of this type? Yes, that is a viable consequence. A law should be made to provide everyone with equal insurance rights. 

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