PCB 3063 Lecture Notes - Lecture 11: Start Codon, N-Formylmethionine, Reading Frame
Genetic Code is...
-Unambiguous
-Degenerate (18 A.A. specified by more than one triplet)
-Commaless (no internal punctuation)
-Non-overlapping
-Nearly Universal
Codons come in...
Triplets
T/F: you can have more than one triplet combination for a single amino acid but not more than one
amino acid for a single triplet combination
True
How did we figure out codons come in 3's?
Brenner was the first to argue the triplet theory.
Acridine dyes- one insertion followed by deletion restores reading frames, as does 3 insertions or 3
deletions affect only 2 codons
How did they disprove overlapping theory of codons?
Consider: GTACAA
We read GTA then CAA
but the thought of overlapping is reading GTA then TAC then ACA, but the problem with that is that it
would limit the # of amino acids that could be coded for, and it would mean that a single mutation
would affect 2 genes.
In a solution of A:C in 1:5 there is
5/6ths C in the code and 1/6th A in the code.
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Document Summary
Degenerate (18 a. a. specified by more than one triplet) T/f: you can have more than one triplet combination for a single amino acid but not more than one amino acid for a single triplet combination. Brenner was the first to argue the triplet theory. Acridine dyes- one insertion followed by deletion restores reading frames, as does 3 insertions or 3 deletions affect only 2 codons. In a solution of a:c in 1:5 there is. 5/6ths c in the code and 1/6th a in the code. Usually the third position of the codon triplet is the least important. Meaning there is a bit of leeway for trna when it binds to the codons because if it can make the two correct h-bonds and the last one kinda doesnt work its still attached enough. Also lowers the chance that a mutation in one of codons will be detrimental.
