Concept explainers
To write: A short essay to explain the molecular and cellular events leading to the heterozygotes individuals in sickle cell trait leading to the individual and population levels of biological organisation. .
Introduction:
Sickle cell disease is the most commonly occurring recessive inherited disorder found in African – Americans with an incidence of 1/400 and a carrier frequency of 1/10. It is caused due to the sickle cell allele that results in the structural and functional abnormality in normal haemoglobin. A point mutation that causes the substitution of glutamic acid by valine at 6th position of β-globin chain of haemoglobin is the main cause. The homozygous recessive individuals suffer severely from the disease; however the heterozygous carriers have the benefit of killing the malarial
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BIOLOGY DUAL ENROLLMENT VERSION
- Sickle cell anemia patients suffer from a distorted red blood cell shape and an anemic condition as a result of a genetic mutation in the HBB gene, which codes for the hemoglobin β subunits. This mutation changes a Glu to a Val at position 6 in the protein, and these patients express two alleles (one from each parent) with this mutation. When individuals inherit just one copy of this mutated gene, they are considered carriers, and have very few symptoms. Based on the quaternary structure of hemoglobin, what can you predict about the assembly of hemoglobin in sickle cell anemia patients versus carriers of the sickle cell trait? a. In sickle cell anemia patients, the α globin subunits have complementary mutations to ensure the quaternary structure of hemoglobin is attained. b. In sickle cell anemia patients, 100% of the hemoglobin is fully functional, whereas in those that carry the trait, there is no functional hemoglobin assembled. c. In individuals with the sickle cell…arrow_forward4. You are to choose the members of an expedition that will climb several high mountains. Each applicant for one of the positions is a heterozygote for an abnormal hemoglobin: Person A: Hb Albany: a methionine has been substituted for Lys 82 in the B-subunit. Person B: Hb Cowtown: a leucine has been substituted for His 146 in the B-subunit. Person C: Hb Flagstaff: an isoleucine has been substituted for Val 1 in the B-subunit. For the locations of the amino acid residues refer to your text, the figure on page 9 of this lab, and the KING exercises. Assuming that each of these candidates is equal in ability at low altitude, which one would you choose for the expedition? To answer this question, determine how the substituted amino acid affects the structure and function of each abnormal hemoglobin, and describe the physiological effect. Focus on the stabilization of the T versus R state of hemoglobin, and the consequent physiological changes that might occur altitude. Keep your answers…arrow_forward. The mutation causing sickle-cell anemia in humans, which changes the normal T to an A in the sixth codon (substituting valine for glutamic acid), occurs in which gene of the hemoglobin family? the a-globin gene (alpha) the b-globin gene (beta) the g-globin gene (gamma) the d-globin gene (delta) the e-globin gene (epsilon)arrow_forward
- . Suggest probable conseauences of the following real or possible hemoglobin mutations. (a) At B146 (HC3) His → Asp (b) At B92 (F8) His Leu In each case, tell whether a single-nucleotide change is sufficient for the mutation.arrow_forward. Mutations in an autosomal gene in humans cause aform of hemophilia called von Willebrand disease(vWD). This gene specifies a blood plasma proteincleverly called von Willebrand factor (vWF). vWFstabilizes factor VIII, a blood plasma protein specified by the wild-type hemophilia A gene. Factor VIIIis needed to form blood clots. Thus, factor VIII is rapidly destroyed in the absence of vWF.Which of the following might successfully be employed in the treatment of bleeding episodes in hemophiliac patients? Would the treatments workimmediately or only after some delay needed forprotein synthesis? Would the treatments have only ashort-term or a prolonged effect? Assume that allmutations are null (that is, the mutations result in thecomplete absence of the protein encoded by the gene)and that the plasma is cell-free.a. transfusion of plasma from normal blood into avWD patientb. transfusion of plasma from a vWD patient into adifferent vWD patientc. transfusion of plasma from a hemophilia A…arrow_forwardA genetic variant of the HBB gene results in sickle cell anemia, a disorder than primarily affects people of Sub-Saharan African descent, including many black Americans. Sickle cell anemia is named after the shape of the red blood cells in individuals with this disorder. The diseased genetic variant in the HBB gene results in a malformed hemoglobin protein, which is responsible for the shape of the red blood cell. Patients diagnosed with this disorder often exhibit a variety of symptoms, such as episodes of pain, swelling of hands and feet, delayed growth, and vision problems amongst others. The malformed hemoglobin protein is an example of the relationship between genes and traits at the: molecular level. population level. cellular level. organism level.arrow_forward
- Fetal hemoglobin binds to BPG to a lesser extent than does HbA because His 143 in the BPG binding pocket in β-globin has been replaced with a serine residue in γ-globin. As a result of the loss of two positive charges (one for each of two γ-globins), the binding pocket binds BPG less avidly. What are the consequences of this phenomenon for mother and fetus?arrow_forwardSickle-cell anemia is a genetic disorder of individuals homozygous for a mutation of hemoglobin that causes their red blood cells to be sickle shaped and stiff under conditions of low pO2. Why is this disease life threatening?arrow_forwardDetermine which statements could be used as evidence to support the argument that "DNA influences the proteins that are made" and which statements are just facts. [Select all that apply.] The HBB gene that makes beta-globin has several abnormal alleles, including HbS, HbC, and HbE. Sickle cell disease has been successfully treated using bone marrow transplantation in children and adults. The symptoms of sickle cell anemia may not appear in individuals who only carry one HbS allele, but are always apparent when both alleles are HbS. If oxygen is removed from red blood cells made by two HbS alleles, the cell will form a sickle shape.arrow_forward
- One molecule of 2,3-BPG binds to one tetramer of hemoglobin in a central cavity of the hemoglobin molecule. Is the interaction between BPG and hemoglobin stronger or weaker than it would be if BPG bound to the surface of the protein instead? Explain your answer (hint: think about how these different situations affect the dielectric constant).arrow_forwardFill in the blanks to describe the sequence of molecular events that follow the binding of oxygen molecule to the first binding site in deoxy hemoglobin and lead to a T to R conformational change. Oxygen binds to one of the Hb subunits causing the coordination bond to move as well. This in turn causes an to move about 0.4A, causing that interacts with it via a which is part of the same alpha helical segment as to move away from a nearby positively charged residue. As a result, this residue and an ion pair that stabilises (intra or inter ?) subunit contacts is broken, inducing the movement of C-terminus of the Hb subunit to which oxygen bound toward the (center / edge?) of the Hb tetramer. This alters the overall fold of Hb monomers from to form and causes 2,3 BPG to Give you answers is a numbered list starting from 1arrow_forwardThere is a benign congenital condition called Hereditary Persistence of Fetal Hemoglobin (HPFH) in which production of the fetal hemoglobin (HbF) is not switched off post-partum (after birth). It is due to a mutation in the β-globin gene cluster. People that are homozygotes for this mutation, meaning that the gene from both parents is mutated, continue to make almost exclusively HbF throughout their life rather than adult hemoglobin (HbA). HPFH homozygotes demonstrate a slight erythrocytosis, or an increase in the number or mass of their red blood cells, and consequently an increase in the concentration of HbF. Given only what you know about the oxygen saturation dynamics of HbF versus HbA, can you explain why there might be the slight erythrocytosis in HPFH homozygotes? It has been observed that the prevalence of HPFH is much higher in populations with certain hemoglobinopathic disorders such as sickle cell anemia, and is selected for in populations with a high prevalence of these…arrow_forward
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