Q NBME F1 S4

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Q NBME F1 S4

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bluestar
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07/26/04 - 11:50 PM

The nucleotide sequence encoding four amino acids near the amino terminus of a 10-kd protein is 5' - ACT GAT TGC GTT -3'. This sequence is mutated by insertion of a single nucleotide (A) inthe second codon and becomes 5'-ACT GAA TTG CGT -3'. Which of the following consequences of this mutation is most likely?

A) Altered cell-cycle checkpoint
B) Decreased rate of transcription
C) Protein truncation
D) Single amino acid substitution

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adeelmd
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07/27/04 - 10:17 AM

C... i'mm guessing GAA is a stop codon, but i never memorised that cuz i didn't think it was high yield.. oh well sucks for me....

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dariush
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07/27/04 - 06:04 PM

A.this is a Frame shift mutation which almost always makes "Missense" transcription and usually "Nonsense" (premature stop) too which would make C. correct but more importantly it is usually Dysfunctional so if a key enzyme in the check point it could lead to A.

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adeelmd
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07/27/04 - 06:30 PM

just as corollary the three stop codons are Uaa, Uga, and UAG...but I am not sure that question takes lippincott into account..

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bluestar
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07/27/04 - 10:21 PM

"dariush" wrote:
A.this is a Frame shift mutation which almost always makes "Missense" transcription and usually "Nonsense" (premature stop) too which would make C. correct but more importantly it is usually Dysfunctional so if a key enzyme in the check point it could lead to A.

but we can't assume it's a key enzyme in cell cycle so I guess it's safe to choose C?

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dariush
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07/28/04 - 04:52 PM

but how would u exclude that option bluestar?

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