question about frameshift mutations and what changes the reading frame.

[mrh125]

ok frameshift mutations can be particularly problematic because they shift the entire reading frame. Would a deletion or addition of 3 bases shift the reading or retain it? (i'm thinking retain) I know additions or deletion of two bases would alter the reading frame, but im think as long as it is in done in a multiple of three the reading frame is retained. help?

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[rodmichael82]

ok frameshift mutations can be particularly problematic because they shift the entire reading frame. Would a deletion or addition of 3 bases shift the reading or retain it? (i'm thinking retain) I know additions or deletion of two bases would alter the reading frame, but im think as long as it is in done in a multiple of three the reading frame is retained. help?

Yes frame shifts happen with any type of deletion or insertion other than 3 nucleotides. The DNA will be transcribed and give you mRNA, then the mRNA will be translated. When the translation occurs and you form proteins the tRNA anti-codon will look at 3 codons on the mRNA to give you one Amino Acid. So technically if you deleted or inserted based on 3 nucleotides in the first place then you will be either removing an amino acid, adding it or possibly nothing at all (if it's a silent mutation).

 

[mcloaf]

Addition of 3 nucleotides or the subtraction of 3 nucleotides does not generally cause a mutation because the reading frame is not shifted.

You're changing the genetic code, by definition it's a mutation. However, you're right in that chances are much higher it will end up being a silent mutation assuming it's at a non-critical residue.

 

[mcloaf]

http://www.bio.brandeis.edu/classes/biol122a/Lecturerepeats.htm

under 1. Frameshifts part a:
"Frameshifts therefore cause, in general, very severe phenotypic effects.Addition or subtraction of 3 nucleotides does not generally cause a mutation because the reading frame is not shifted."

Seriously? You quoting a resource that is also wrong doesn't make you right.

As I said before, a change in the genetic code is, by definition, a mutation. A mutation doesn't have to cause a change in the protein product of a gene. With your definition there would be no such thing as a silent mutation because the protein product is maintained.

 

[dyspareunia]

Addition of 3 nucleotides or the subtraction of 3 nucleotides does not generally cause a mutation because the reading frame is not shifted.

Please get out of here with this bs info. Yes any change involving a factor of 3 nucleotides is not a frameshift mutation, but it is a mutation of some kind.