New outcomes in mutation rates analysis

The GC-content is very variable in different genome regions and species but although many hypothesis we still do not know the reason why. Here we show that a relationship exists with the mutation rate, in particular we noticed a new recurrence in the amino acids coding table. Moreover we analyze recombination frequency taking into account Single Nucleotide Polymorphisms hourglass distribution. The reason of the high variability in the GC-content between species remains unclear. As mentioned by [1], many hypothesis have been postulated during the years by many groups, such as UV resistance [2][3] , thermal adaptation [4][5], directional mutation pressure [6], metabolism[7], the length of coding sequences [8][9], nitrogen fixation [10], aerobiosis [11], environment pressure [12], genome size [13] and DNA polymerase III [14]. What we know for sure is that chromosomal bands reveal different compositions in G+C and that the gene density in the GC-richest fraction of the human genome is known to be higher than in the poorer GC regions [15]. Amino acids coding table evolved to minimize mutations therefore this codons organization suggests C↔T and A↔G mutations to be more frequent. In his storic paper " Codon—anticodon pairing: The wobble hypothesis " [16], Crick suggests that, due to the degeneracy of the genetic code, wobble base pairs are fundamental for the proper translation of the genetic code. So that while the first two positions of the triplet are critical, there may be some wobble in the pairing of the third base. In other words, the third base is considered to be less discriminatory than the other two bases. However, if we look at the amino acids coding table (Figure 1) and we focus on amino acids encoded by two different triplets that the triplets can be divided into 2 categories: codons which third nucleotide can be U or C (pink circles), and codons which third nucleotide is A or G (purple circles). This cannot be due to casuality. Here we hypothesis error correction to explain the dilemma. The determinant factors could be the number of bonds (each couple includes a nucleotide that forms 3 bonds and a nucleotide that forms 2) or the nucleotide formula (purines or pirimidines). Moreover, we hypothesize polymerase mutations of a 3-bonds-forming-nucleotide to a 2-bonds-forming-nucleotide – from now we will call this type of 32 – to be not only the more conserved but the more probable too. The neutral theory of molecular …