Lecture11

Lecture11 - Lecture11 Background reading Berg et al Pages...

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Unformatted text preview: Lecture11 10/17/11 Background reading: Berg, et al. Pages 182 - 188 Garrett and Grisham: pages 132 - 143 Outline: ¡ Fetal hemoglobin ¡ Detrimental mutations of hemoglobin genes ¡ Origin of protein diversity ¡ Intragenic mutation ¡ Cytochrome ¡ Gene duplication ¡ Segment shuffling ¡ Protein domains ¡ Immunoglobulin G ¡ Fibronectin • Fetal hemoglobin Fetal hemoglobin is a tetramer containing two α- chains and two γ-chains. The γ- chain has 72% identity in amino acid sequence with the β-chain. This difference in sequence does not enable fetal hemoglobin to bind to 2,3-BPG as well as adult hemoglobin and as a result the fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin. The mother can thus transport oxygen from her hemoglobin to the fetus hemoglobin. • Detrimental mutations of hemoglobin genes About 7% of the world population carry disorders in sequence of hemoglobin genes. Example: Sickle cell anemia A single substitution of a glutamate residue at position 6 of the β-subunit with valine produces a mutated form, called hemoglobin S. This residue is on the surface of the T form of hemoglobin and can interact with two hydrophobic residues on the β-chain of a neighboring molecule to aggregate hemoglobin fibers. This happens only in the T form and not in the R form of the molecule. People with this disease have the mutation in both alleles of the gene for the β-chain. People with only one allele mutated are carriers of this mutation, but have been found to be resistant to the parasite that carries malaria and this resistance is most probably why this mutated gene has remained prevalent in some areas of the world. ¡...
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Lecture11 - Lecture11 Background reading Berg et al Pages...

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