Several techniques have been developed to treat blood disorders caused by genetic mutations. Which of the following methods would be most effective in the treatment of a patient homozygous for a deleterious mutation in a gene coding for a subunit of hemoglobin?

Question

Several techniques have been developed to treat blood disorders caused by genetic mutations.  Which of the following methods would be most effective in the treatment of a patient homozygous for a deleterious mutation in a gene coding for a subunit of hemoglobin?

Quizplus · Accepted Answer

11ecba2d_1032_9e19_a3bf_3b151679b445_MD0008_00 Hemoglobin is an oxygen-binding protein found within red blood cells (RBCs). Oxygen diffuses into the bloodstream via gas exchange in the lungs, binds hemoglobin, and is transported through the circulatory system to tissues throughout the body. Deleterious mutations affecting hemoglobin genes may negatively impact hemoglobin function, impairing oxygen transport. One method of treating genetic mutations is gene therapy, a technique in which a functional gene is introduced into a patient's cells to replace a mutant gene. The new gene can then be transcribed and translated into functional proteins. A common gene therapy method uses retroviral vectors to insert functional gene copies into the stem cells of patients exhibiting specific genetic mutations. In this scenario, a patient is homozygous for a deleterious mutation in a gene coding for a hemoglobin subunit. Expression of this mutant gene would likely produce a portion of the hemoglobin protein with impaired function. Because RBCs are produced from stem cells in the bone marrow, the most effective treatment for this patient would be gene therapy to introduce and activate a functional hemoglobin gene in bone marrow stem cells. This would likely lead to the production of RBCs that contain hemoglobin with normal oxygen-binding abilities. (Choice A) The mutant gene could not be replaced by a functional copy in mature RBCs because mature RBCs lack nuclei and do not contain DNA. (Choice B) Treatment with a drug that increases RBC production would increase the differentiation of bone marrow stem cells into mature RBCs. However, because this treatment does not introduce a functional copy of the hemoglobin gene, these cells would still express the mutation as well as functionally impaired hemoglobin. (Choice D) A blood transfusion from a patient homozygous for the wild-type hemoglobin gene may introduce RBCs expressing functional hemoglobin into the patient's bloodstream. However, all aging RBCs are eventually destroyed by phagocytic cells (ie, macrophages) in the spleen. Because RBCs with wild-type hemoglobin would eventually be destroyed, the patient would require multiple blood transfusions to maintain a population of healthy RBCs. Educational objective: Gene therapy is a technique in which a functional copy of a gene is introduced (eg, via retroviral vectors) into the cells of a patient with a mutation in that gene.

Several Techniques Have Been Developed to Treat Blood Disorders Caused