In which disorder do neonates demonstrate the presence of Bart's hemoglobin that changes to beta chain tetramers in adults? Please select the single best answer Alpha thalassemia major Alpha thalassemia minor Hemoglobin H disease Hydrops fetalis
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Bart's hemoglobin is a tetramer of gamma chains ($\gamma_4$). It is present in neonates with alpha thalassemia, specifically in cases where there is a severe deficiency of alpha globin chains. In adults, the hemoglobin tetramers are composed of alpha and beta Show more…
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Alpha thalassemia is a blood condition resulting from abnormal hemoglobin production, due to loss of function of copies of either HBA1 or HBA2 genes. These genes are very similar, and for simplicity's sake, we talk about having four copies of the HBA gene (two copies of each). HBA1 and HBA2 genes are located next to each other and therefore are described within the same allele. For example, αα indicates that both HBA1 and HBA2 copies on an allele are functioning, α- indicates an allele with one of the two genes functioning, and -- indicates an allele with neither gene functioning. There are multiple versions of alpha thalassemia, which depend on how many of the four HBA copies are functioning. This is outlined in the table below, in order of severity (most severe -> least severe): Phenotype Genotype α-thalassemia major Loss of all 4 α-globin genes Hemoglobin H (HbH) disease Loss of 3 α-globin genes α-thalassemia trait Loss of 2 α-globin genes in cis (--/αα) or trans (-α/-α) α-thalassemia silent carrier Loss of 1 α-globin gene (-α/αα) A man who is a silent carrier has a child with a woman who has α-thalassemia trait. a) Assuming the woman has mutations in cis, what are the possible offspring phenotypes for this child? Give the probability for each possible phenotype. b) Assuming the woman has mutations in trans, what are the possible offspring phenotypes for this child? Give the probability for each possible phenotype.
Adi S.
13. Which process is most responsible for the sickling of cells seen in sickle cell disease? A) aggregation of the oxygenated R form of hemoglobin-S to form insoluble fibers B) aggregation of the deoxygenated T form of hemoglobin-S to form insoluble fibers C) Hemoglobin-S does not contain heme D) Hemoglobin-S contains a mutant form of heme which will not bind oxygen. 14. A person with sickle-cell trait is very unlikely to catch which disease? A) malaria B) colon cancer C) avian flu D) whooping cough. 15. A person with a genetic defect which results in the synthesis of an insufficient amount of the alpha chain of hemoglobin is said to have which disease? A) alpha thalassemia B) beta thalassemia C) pernicious anemia D) Crohn's disease.
Sukhada S.
1. What protein switches off the production of fetal hemoglobin after birth? 2. Complete the following sentences by circling the correct term in parentheses: When BCL11A protein production is high, then fetal hemoglobin production is (low). When BCL11A protein production is low, then fetal hemoglobin production is (high). Therefore, to increase fetal hemoglobin production after birth, scientists want to (decrease) the production of BCL11A protein in red blood cells. b. Which DNA sequence is being targeted for genome editing in the first clinical trial using CRISPR/Cas to cure sickle cell disease? a. β-globin gene b. γ-globin gene c. BCL11A regulatory DNA
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