Sickle Cell Anemia / Cystic Fibrosis?
A question from justgoo: Sickle Cell Anemia / Cystic Fibrosis?
There is one specific DNA change associated with the allele which causes sickle cell anemia but there are several alleles which cause cystic fibrosis, each with specific DNA changes. What may explain this difference?
a. The sickle cell anemia allele makes a product which functions normally under some conditions and abnormally under others. This is unusual and only one allele has been found to produce such an effect for the β globin gene.
b. Cystic fibrosis can be caused by lack of the normal protein or a decrease in the protein function produced by this gene and a number of mutations at different sites can produce abnormal protein products.
c. Cystic fibrosis is one phenotype that can be caused by a number of different genes. Any gene that causes cystic fibrosis has only one abnormal allele.
d. A and b are true.
e. A and c are true.
Chosen answer:
Answer by michelle k
A and C (so the answer would be E). this has to do with whether the disease is caused by one gene or the effect of many genes. I think (BUT I AM NOT SURE) that sickle cell anemia is caused by a defect in ONE gene and then produces effects that can helpful or harmful under certain conditions. it leads to a heterozygote advantage, in which people that live in malaria infested areas live longer. And I think cystic fibrosis is caused by a problem in many genes. Hope this helps. BUT I AM NOT ENTIRELY SURE.
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Tagged with: Anemia • Cell • cystic • fibrosis • Sickle
Filed under: Cystic Fibrosis
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The answer is “d”, both A and B are true. Sickle cell anemia is caused by mutations in the beta-globin gene and the mutated globin product doesn’t work as well as the normal protein. It causes changes in the folding of the hemglobin which leads to the characteistic sickle shape of the erythrocytes. The mutation however, does make these erythrocytes more resistant to the malaria parasite, providing an advantage for keeping this “allele”.
As for cystic fibrosis, the problem arises when the cells of the epithelia can not transport chloride ions efficiently out of the cell through the CFTR protein. Different mutations within the CFTR gene that affect the ability of the CFTR protein to do its normal function will lead to cystic fibrosis. THis could be the result of decreased efficiency for chloride transport or decreased amount of stable CFTR in the cells.
As for ‘c’, there is no a priori reason to assume that any gene that can cause cystic fibrosis would have only one type of mutated allele.