AAMC FL2 #43 Searched but still stumped. How can a frame shift mutation NOT affect the stop codon?

[letsgetstarted1234]

So they insert a nucleotide to the mRNA.
But in trying to understand what happens, how can a frameshift NOT affect the stop codon yet have the same start codon (thats what they mean by amino sequence right?)
Stop Codons are:
UAG
UAA
UGA
If I insert a nucleotide anywhere after the starst codon, its going to shift as follows:
before addition:
AUG-AAA-AAA-AAA-UAG (or UGA or UAA)
after addition:
AUG-AAA-AAA-AA**U**-AUA-G
No matter what nucleotide is before the stop codon, you can't still have a stop codon at the same place.
UAG
UAA
UGA
U can never be the second nucleotide in the stop codon, so shifting everything down one has to affect the stop codon.
I must be interpreting this wrong?

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[sillyxwabbit]

So they insert a nucleotide to the mRNA.
But in trying to understand what happens, how can a frameshift NOT affect the stop codon yet have the same start codon (thats what they mean by amino sequence right?)
Stop Codons are:
UAG
UAA
UGA
If I insert a nucleotide anywhere after the starst codon, its going to shift as follows:
before addition:
AUG-AAA-AAA-AAA-UAG (or UGA or UAA)
after addition:
AUG-AAA-AAA-AA**U**-AUA-G
No matter what nucleotide is before the stop codon, you can't still have a stop codon at the same place.
UAG
UAA
UGA
U can never be the second nucleotide in the stop codon, so shifting everything down one has to affect the stop codon.
I must be interpreting this wrong?

Hey, so you're pretty close!
so when they refer to a amino-terminal and a carboxy-terminal sequence, they're referring to the beginning and ending areas of the entire sequence.
We always read amino acid sequences from N- terminal (amino) to C-Terminal (carboxy).
So exactly, the frameshift will most likely affect areas after the mutation near the C-terminal but most likely did not affect the areas before the mutation near the N-terminal.

Hopefully I have that right.

 

[CommyO]

I think it's just referring to the unaltered start codon. Since the change did not alter or create a start codon, one can conclude that the N term is unaffected. Furthermore, the downstream C-term must be affected due to the insertion

C/D are not true because of only one nucleotide insertion