Concept explainers
A 30-year-old woman was undergoing therapy for β-thalassemia, a recessive trait caused by absence of or reduced synthesis of the hemoglobin p chain, a subunit of the oxygen-carrying molecule in red blood cells. In this condition, red blood cells are rapidly destroyed, freeing a large amount of iron, which is deposited in tissues and organs. The blood transfusions the patient had received every two or three weeks since the age of 7 to stave off anemia were further aggravating iron buildup. Her major organs were showing damage, and she was in danger of death from cardiac disease. Her physician suggested that she consider undergoing a hematopoietic (bone marrow) stem cell transplant (HSCT). Since these stem cells give rise to red blood cells, such a transplant could potentially restore her health. While this might seem like an easy decision, it is not. Advanced cases have a high risk (almost 30 percent) for transplantation-related death. At this point, the woman is faced with a difficult and important decision.
Why is it important that the physician emphasize to the patient that she must bear the responsibility for the final decision (i.e., that once she has considered all aspects of the decision, she act autonomously)?
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EBK CONCEPTS OF GENETICS
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- The proximal histidine residues have been replaced by glycine residues by mutation of the cloned genes for both the α and β subunits of hemoglobin. With the tetrameric mutant hemoglobin (all subunits being mutant, α H F8 G, β H F8 G), it was found that the “proximal” coordination bonds to hemes in the mutant protein could be replaced by having the small molecule imidazole in the buffers. Oxygen binding curves for the tetrameric mutant hemoglobin were measured. A. The degree of cooperativity in oxygen binding for the mutant hemoglobin (with imidazole present) would be expected to 1) increase 2) decrease 3) not be affected) compared with the normal protein. B. Justify your answer to part A in terms of what you know about the structural basis of cooperativity in hemoglobin. C. How would the Hill coefficient for the mutant be expected to change compared with nH for normal hemoglobin, which is ~3?arrow_forwardTwo possible point mutations are the substitution of lysine for leucine or the substitution of serine for threonine. Which is likely to be more serious and why?arrow_forwardDiamond–Blackfan anemia (DBA) is a rare, dominantgenetic disorder characterized by bone marrow malfunction,birth defects, and a predisposition to certaincancers. Infants with DBA usually develop anemia in the firstyear of life, have lower than normal production of red blood cellsin their bone marrow, and have a high risk of developing leukemiaand bone cancer. At the molecular level, DBA is causedby mutations in any one of 10 genes that encode ribosomalproteins. The first-line therapy for DBA is steroid treatment,but more than half of affected children develop resistance tothe drugs and in these cases, treatment is halted. DBA can betreated successfully with bone marrow or stem cell transplantsfrom donors with closely matching immune system markers.Transplants from unrelated donors have significant levels ofcomplications and mortality. Given that a faulty ribosomal protein is the culprit and causesDBA, discuss the possible role of normal ribosomal proteins.Why might bone marrow cells be…arrow_forward
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