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Discussion Starter · #1 ·
The DNA sequence M, shown below, is the sense strand from a coding
region known to be a mutational “hot spot” for a gene. It encodes amino
acids 21 to 25. Given the genetic and amino acid codes CCC = proline (P),
GCC = alanine (A), TTC = phenylalanine (F), and TAG = stop codon,
which of the following sequences is a frame-shift mutation that causes termination
of the encoded protein?
M 5′-CCC-CCT-AGG-TTC-AGG-3′

a. -CCA-CCT-AGG-TTC-AGG
b.-GCC-CCT-AGG-TTC-AGG
c.-CCA-CCC-TAG-GTT-CAG
d.-CCC-CTA-GGT-TCA-GG—
e. -CCC-CCT-AGG-AGG——
 

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Discussion Starter · #2 ·
Insertion (choice c) or deletion (choice d) of
nucleotides shifts the reading frame unless the change is a multiple of 3
(choice e). Frame shifts may create unintended stop codons as in choice c.
Point mutations resulting in nucleotide or amino acid substitutions are
conveniently named by their position in the protein, i.e., P 21 A (choice b).
The protein change P 21 A could also be denoted by the corresponding
change in the DNA reading frame, i.e., C 63 A. Deletions may be prefixed by
the letter delta, as with ∆F 25 (choice e).


i cant understand what is c63a ??
but i think may be p is proline 21 A is alanine.. pls explain me :
The protein change P 21 A could also be denoted by the corresponding
change in the DNA reading frame, i.e., C 63 A."
 
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