Plausible sources of mono, di, tri, & tetra- nucleotide biases
C rare due to lack of uracil glycosylase (cytidine deamination)
TT rare due to lack of UV repair enzymes.
CG rare due to 5methylCG to TG transitions (cytidine deamination)
AGG rare due to low abundance of the corresponding Arg-tRNA.
CTAG rare in bacteria due to error-prone "repair" of CTAGG to C*CAGG.
AAAA excess due to polyA pseudogenes and/or polymerase slippage.
AmAcid Codon Number /1000 Fraction
Arg AGG 3363.00 1.93 0.03
Arg AGA 5345.00 3.07 0.06
Arg CGG 10558.00 6.06 0.11
Arg CGA 6853.00 3.94 0.07
Arg CGT 34601.00 19.87 0.36
Arg CGC 36362.00 20.88 0.37
ftp://sanger.otago.ac.nz/pub/Transterm/Data/codons/bct/Esccol.cod