BIOL 1010 Study Guide - Midterm Guide: Sickle-Cell Disease, Online Mendelian Inheritance In Man, Base Pair

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19 Dec 2015

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Sickle cell anemia is a well-known disease that is caused by a mutation in a single gene. It is the most common inherited blood disorder in the united states (national center for. This disease affects the protein found in red blood cells that transports oxygen throughout the body, known as hemoglobin. Some common symptoms are periods of pain, chronic hemolytic anemia and severe infections. This signs are usually noticed in early childhood (kniffin, 2013). The clinical feature of sickle cell anemia is vaso-occlusive crisis. A vaso-occlusive crisis is when blood vessels are clogged, causing severe injury to the organ and extreme pain (national. These series of pain are also a clinical feature of sickle cell disease. Unfortunately, pain is the leading cause of emergency department visits and hospitalizations for affected patients. The inheritance of the disease is similar to most single gene mutations; it is autosomal recessive.

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Questions 4-6. Sickle cell disease:
Sickle cell disease (sickle cell anemia) is a relatively common disorder in individuals of

African descent and affects approximately 1 in 500 African-Americans. Due to a mutation in an autosomal gene for hemoglobin, the homozygous recessive genotype leads to red blood cells that are relatively stiff and sticky, and deform into a sickle shape as they lose oxygen. This leads to problems in the spleen, and anemia.

There are hundreds of different hemoglobin alleles. Individuals heterozygous for the sickle cell allele and one non-sickle cell allele usually do not experience major complications or even noticeable symptoms. A genetic test is available to diagnose carriers.

James does not have sickle cell disease, neither does his mother or father, but his sister does. His wife Natasha does not have sickle cell disease, and neither of her parents does either. Natasha also has a sister who has sickle cell anemia and two brothers without the disease.

5.) If James and Natasha have a child, what is the probability that the child would be a homozygote for the recessive allele and have sickle cell disease? You may draw the Punnet square but please solve the problem using probability calculations, then explain your reasoning in 2-5 complete sentences.

cyanalligator893

1. Sickle cell was the first disease characterized at the molecular level. Using appropriate molecular genetic terminology connect the genotype to the phenotype for sickle cell anemia.

2. What selective advantage that comes from the organization of âgenes in piecesâ found in Eukaryotic cell?

Normal adult hemoglobin is called Hemoglobin A (Hb A). Ninety-eight percent of adult hemoglobin is Hb A and 2% is Hb A2. There are other forms of hemoglobin. For example, the developing fetus has a different kind of hemoglobin than most normal adults. Fetal hemoglobin (Hb F) is synthesized beginning at the third month of gestation and continues up through birth. After the neonate is born, hemoglobin F synthesis declines (because synthesis of the (chain declines) and hemoglobin A is synthesized. By the time the baby is six months old, 98% of its hemoglobin is Hemoglobin A. There is also a mutant form of hemoglobin called Hemoglobin S, which is found in persons with the disease sickle cell anemia. The disease sickle cell anemia is one of the major health problems facing the African-American community. The World Health Organization estimates that 250,000 babies world wide are born with sickle cell anemia. Currently there is no cure. A person afflicted with sickle cell anemia has inherited a defective gene from each parent. The defective gene is the one coding for the Î²-chain. The amino acid at position 6 on each Î² chain has been mutated from a glutamate to a valine. Normal Î± chains have a decreased affinity for the mutated Î² chains; thus assembly of the HbS tetramer is more difficult. Red blood cells containing HbS form a sickle shape because the Hb S molecules polymerize. Hb S molecules are more likely to polymerize when in the deoxygenated T form than in the oxygenated R form. The polymerized Hb deforms the normal discoid shape of the red blood cells, producing a sickle-shaped cell. The sickle shaped red blood cells become trapped in capillaries and organs, depriving the victim of adequate oxygen supply and causing chronic pain and organ damage.

Glover, R. E., Ivy, E. D., Orringer, E. P., Maeda, H., and Mason, R. (1999) Molecular Pharmacology 55, pp. 1006-1010.

Huang, J., Hadimani, S. B., Rupon, J. W., Ballas, S. K., Kim-Shapiro, D. B., and S. Bruce King (2002) Biochemistry 41, pp. 2466-2474.

S. Bruce King (2003) J.Clin. Invest., 111, pp. 171-172.

1) Why do you think Hb S has higher tendency to polymerize compared to Hb A?

BIOL 1010 Study Guide - Midterm Guide: Sickle-Cell Disease, Online Mendelian Inheritance In Man, Base Pair

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