I work on Bioinformatics system for mutation detection in TP53, I would like to know the possible number of mutation per a codon i.e.:
Codon 248 consist of three bases of amino acid which is:
CGG
the mutation can be in only one base? such as:
CGG ---> CGC
or
CGG ---> GGG
and so on
Is it possible to have Mutation in two bases or more?
CGG ---> GCG
CGG ---> CAA
what will happen if the Mutation occurred in the three bases?
CGG ---> GCC
CGG --->TAC
Of course it is "possible" to have any number of mutations, and also to have deletions or insertions as well as single base changes. However it is very very highly unlikely for two single base changes to happen in the same codon in a short period of time. Also, in most organisms the rate of transitions (purine for purine or pyrimidine for pyrimidine) is 2 to 20 fold higher than the rate of transversions. On top of this there are huge differences in selection pressures after the mutation happens depending on the system you are working in.
There are 64 possible combinations of nucleotides for three consecutive positions. The complete list of combinations and the corresponding amino acids can be found here:
https://en.wikipedia.org/wiki/DNA_codon_table
since the classical Dayhoff table 1979, numerous matrices have been given (see the following links) ; these are mostly substitution matrices but you will find equivalent for indel mutations.
http://steipe.biochemistry.utoronto.ca/abc/index.php/Mutation_Data_Matrices
https://www.genome.jp/aaindex/AAindex/list_of_matrices
As indicated in the other comments, there are multiple possibilities to have variations in a single codon of any gene; If I go deeper in your question, it is specific for the TP53 gene and if I understand the ultimate meaning of the question it is related to the possible selection of TP53 variants in human cancer for each codon.
The answer is more complex as i) Variant observed in human cancer have been selected for loss of function mutation and ii) the mutagenic process is highly selective as most mutations will only target a single nucleotide. It is very unfrequent to have tandem mutation (modification of two adjacent nucleotides) except in skin cancer and triple nucleotide substitution have never been observed.
Therefore, for TP53 in human cancer, you will see predominantly single nucleotide substitutions leading to missense or nonsense variants.
T Soussi
TP53 mutation database curator
You could have several number of mutations in a codon. Mutations in a codon most likely would be from single base changes and also, deletion or insertion of a single base as stated in a comment earlier. However, frame shift changes in the nucleotide sequence could also introduce mutations in the codon.
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