Table 2 Comparison of conserved optimal codon numbers at paired and unpaired sites.

Amino acids with GC-ending optimal codons

Leu _TTG

1.380 ***

1.273 ***

1.811 ***

1.456 ***

Lys _AAG

1.772 ***

1.654 ***

2.019 ***

1.654 ***

Phe _TTC

1.075 ***

1.120 ***

0.786 NS

0.864 **

Tyr _TAC

0.809 NS

0.720 NS

0.741 NS

0.631 NS

His _CAC

0.707 NS

0.600 NS

0.568 NS

0.657 *

Asp _GAC

0.813 NS

0.838 NS

0.656 ***

0.746 **

Asn _AAC

0.891 *

0.831 NS

0.725 **

0.637 NS

Amino acids with one GC- and one AT-ending optimal codon

Ile _ATC

1.318 ***

1.254 ***

1.555 ***

1.049 ***

Ile _ATT

1.272 ***

0.978 ***

1.561 ***

1.009 ***

Val _GTC

0.585 NS

0.852 ***

0.734 ***

0.560 ***

Val _GTT

0.705 *

0.794 NS

0.806 *

0.686 NS

Thr _ACC

0.838 **

0.921 ***

0.811 ***

0.750 ***

Thr _ACT

0.940 ***

0.876 ***

0.932 ***

0.655 ***

Ser _TCC

0.614 NS

0.668 NS

0.583 NS

0.591 NS

Ser _TCT

0.794 NS

0.816 NS

0.816 ***

0.985 ***

Amino acids with AT-ending optimal codons

Ala _GCT

0.968 **

0.904 ***

1.073 ***

0.883 ***

Arg _AGA,CGT

0.588 ***

0.545 ***

0.518 ***

0.460 ***

Gly _GGT

0.894 NS

0.779 NS

0.901 ***

0.752 NS

Gln _CAA

0.442 ***

0.353 ***

0.293 ***

0.278 ***

Glu _GAA

0.946 ***

0.350 ***

0.386 ***

0.315 ***

Pro _CCA

0.851 NS

0.734 NS

0.729 **

0.689 *

Cys _TGT

0.500 NS

0.382 NS

0.755 ***

0.403 NS