4 ms·
What? You start with a two-letter code, then something evolves that puts an (initially) rare third letter at a few locations on the tape. All the old "gear" t
by adrianratnapala 8y ago
What?
You start with a two-letter code, then something evolves that puts an (initially) rare third letter at a few locations on the tape. All the old "gear" that reads two-letter code can still read most of the tape.
- rotexo 8y agoIt is difficult to imagine that as a possibility. The spacing of three mRNA nucleotides is pretty important structurally in the process of translation from mRNA to protein via the ribosome. It is difficult for me to imagine a ribosome that could operate arbitrarily between codons of two and three nucleotides, unless I am misunderstanding your comment. A translational reading frame consists of non-overlapping codons of three nucleotides. If one nucleotide is skipped, the entire downstream message is thus garbled. So how would the translational machinery operate if each codon arbitrarily consisted of two or three nucleotides?
- asdff 8y agoI see what you are getting at, but I think what the other comments are saying is that for the third nucleotide position of a given codon, it does not matter which nucleotide this is. The amino acid to be used would only depend on the first two nucleotides, while the third nucleotide can be AUCG.
- adrianratnapala 8y agoNah, I misunderstood completely. I was thinking of how a hypothetical code might, in the abstract have evolved from binary, through ternary up to the (current base-4). I haven't got enough biochem knowledge to speculate how three nucleotides per amino acid can evolve to have three.
- dnautics 8y agoThey have done this with a four letter expanded codon. The fitness of the bacteria tanks.