Codon-anticodon interaction

we can see the anticodon arm of tRNAPhe (the same studied before):

Backbone (imaginary line connecting the phosphates).
Stem (nucleotides with paired bases).
Loop (nucleotides with unpaired bases), except the
anticodon (mG-A-A triplet)
(mG is O2'-methylguanosine-5'-monophosphate)



Now let's a molecular model of the interaction between this anticodon (mG-A-A on tRNA) with an UUU codon (on mRNA).
To better differentiate them, the carbon atoms in tRNA and in mRNA have been coloured.

(Since the methyl group in mG is on the pentose, it does not affect pairing, and mG pairs like G.)
(The complementary codon would be UUC, but thanks to wobbling it is also possible to pair with UUU; these are called synonymous codons, and both code for Phe; this is an example of the degeneration of the genetic code.)

 3  2  1
 tRNA   anticodon  3' -A-A-G- 5'
mRNA   codon 5' -U-U-U- 3'
 1  2  3

Note the hydrogen bonds between bases in codon and anticodon, as well as their confrontation and coplanarity.

highlight
A3U1 pair   remove
highlights
A2U2 pair
G1U3 pair