These diverse genetic code mutations necessarily raise the question of the nature of mechanisms that have preserved an inherently mutable ensemble of encoded amino acids in an unaltered form throughout the ages.
In order to alter the genetic code, mutations are required not only in glutamine tRNAs but also in eRF1 so they no longer recognize TAG and TAA codons.
Exactly the same type of damage – called a cyclobutane dimer (CPD) – is already known to occur directly during sun exposure as the UV rays hit DNA strands and scramble the letters of the genetic code into mutations.
This is important in order to see exactly where in Merrick's genetic code the mutations appear.
'Hybrid speciation' or 'recombinational speciation' is often associated with a mosaic genome (Baack and Rieseberg, 2007; Stukenbrock et al., 2012) and because introgressed genes have been 'pre-tested' by selection, they are more likely to be adaptive than random changes to the genetic code by mutations (Hedrick, 2013).
Most of the alternative genetic codes display mutation loads larger than for the standard code.
Next, we study the effect of the different genetic codes on mutation and translation loads (see Methods).
We have modified the mutation process in order to take into account the genetic code and the mutation bias at the DNA level (see also Ref. [ 53]).
The distribution P(T′ jk < x| X jk = nts, ntv, iid, or fid ) can be easily calculated from the genetic code and background mutation model.
Neutrality of the fitness landscape is assumed here for the sake of simplicity, since otherwise the model would depend on at least two additional parameters, i.e. the smoothness of the fitness landscape and the effective size of the population, making it very difficult to reach clear conclusions about the effect of the genetic code and the mutation bias.
Here we simulate the SCN model with a more realistic mutation process that takes into account the genetic code and represent mutations nucleotide level.
