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Molecular genetic studies are performed on a family with known familial hypercholesterolemia. In this particular family, the defect in the LDL receptor gene involves a messenger mutation near the 11th exon, in the region of homology with epidermal growth factor receptor precursor. A defect at this site would be most likely to produce which of the following effects?
A. Decreased transcription of LDL receptor gene
B. Poor internalization of LDL bound to LDL receptor
C. Poor retention of the LDL receptor in the membrane
D. Reduced binding of LDL
E. Trapping of the LDL receptor in the endoplasmic reticulum
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since messenger mutation involved so ---AAA
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B. Poor internalization of LDL bound to LDL receptor
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In familian hypercholesterolemia.. there are decreased number of ldl receptors on the membranes and therefore less LDL is taken out of the circulation.. which sstays in the circulation and causes pathognomonic signs like lipid deposits in the achilles tendon, under the eyes.. etc..
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Explanation:
The correct answer is E. Familial hypercholesterolemia, which is due to defective function of
the LDL receptor, is an area of intense research. The molecular basis of LDL receptor
abnormalities is becoming better understood, and more than 200 mutations in the gene for the LDL receptor have been identified. The gene has 5 general domains and 18 exons. Defects near exons 7 to 14 (including this case) are in the region of homology with epidermal growth factor receptor precursor. This region of the molecule is needed for dissociation of LDL from the receptor in the endosome. Receptors with a defect in this area (sometimes called class II mutations) also have trouble being initially transported to the Golgi complex (transport-deficiency alleles) and become trapped in endoplasmic reticulum.Decreased transcription of the LDL receptor gene (choice A) is considered a class I mutation and
involves the signal sequence domain near exon 1.
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Thanks for the correct explanation.. shows how much i know.
