new_n_lost
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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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| mytime
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  U getting worse hmmmmm
I'll have to think all day for that one but look what I found. And I want u to tell me why what is answer to this one.
http://www-personal.umich.edu/~lemichae/firstaid/...
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| mytime
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Probably E ....guessing.
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| SILVER
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A ??
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| jean robert
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A??
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| SmokyWaters
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EGFP domain is for the RELEASE OF LDL bound to the receptor
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| SmokyWaters
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so may be B? 
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| SmokyWaters
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LDL receptor has different exons that are
exon 1 has signal sequenece that localizes receptor to ER for transport to cell surface
exon 2-6 probably are for ligand binding region
then there is a beta propeller motif ....
after that exon 7-15 are for EGFP domain...share 30% domain homology with EGF
16 n some part of 17 code for membrane spanning region...so its absence would lead to destabilization of receptor and
some part of 17 and full 18th exon is for cytosolic domain ...that helps the clathrin intake of the receptor
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| SmokyWaters
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so I would say
A. Decreased transcription of LDL receptor gene .... doesnt involve exons
B. Poor internalization of LDL bound to LDL receptor ...I am not sure about this but rulin other options out...I had to opt for this... new...tell us please 
C. Poor retention of the LDL receptor in the membrane.... exon 16-18 mutations
D. Reduced binding of LDL .... exon 2-6
E. Trapping of the LDL receptor in the endoplasmic reticulum...exon 1 mutation
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| SmokyWaters
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its the CLASS V mutation though...
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| new_n_lost
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mytime wrote:
Probably E ....guessing.
U guessed Right Buddy
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| new_n_lost
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this one kinda got me smacked upside. Like I was Totally Clueless.
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| new_n_lost
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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.
Poor internalization of LDL bound to LDL receptor (choice B) is considered a class IV mutation. Such mutations are associated with the membrane-spanning/cytoplasmic domain, specifically near exon 18.
Poor retention of the LDL receptor in the membrane (choice C) is considered a class IV mutation and is associated with the membrane-spanning/cytoplasmic domain, specifically near exons 2-6.
Reduced binding of LDL (choice D) is considered a class III mutation and involves the LDL binding domain near exons 2-6.
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| SmokyWaters
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Poor retention of the LDL receptor in the membrane (choice C) is considered a class IV mutation and is associated with the membrane-spanning/cytoplasmic domain, specifically near exons 2-6.|??????
sure????
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| edie
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My guess was E, based upon the clue Smoky gave: "EGFP domain is for the RELEASE OF LDL bound to the receptor". Mutation here would suppress release of the LDL bound to receptor, therefore, resulting in trapping of the receptor in the ER--->hypercholesterolemia. Good one, NNL 
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