codons

Having 4^3 (64) different codons but only 21 amino acids, some amino acids can be represented by several different codons.

We actually do know something about why the genetic code might have only four codons, and other aspects of its structure.

The original set of 4, with 64 possible codons, usually encode for 20 amino acids (excepting special cases as with selenomethionine).

That De Bruijn sequence is highly similar to the way DNA codons can be read.

Mostly it would stay around the noise floor with ~2.5 of the codons set correctly.

Since 64 is much more than 21, many different codons encode the same amino acid.

So, given a byte sequence from the hard drive (gene on the DNA), we always look at codons (three bits) and can then translate those codons into amino acids.

So really there's six potential different codons that a single basepair might be involved in.

In that case, you have to take codons (sets of 3 bases) and convert to one of the 20 amino acids.

The reason it was in Science was because they did an extremely large-scale test of a whole bunch of different codons on thousands of different gene promoters, and directly quantified the impact of rare codons.

But with 3 DNA letters there exist 4^3 = 64 different codons.

Stamatoyannopoulos now for the first time proved that even though two different codons encode the same amino acids they might attract different transcription factors.

Because 3 out of 64 codons are "stop" codons, almost every frameshift error results in truncation of the affected protein.

Nitpick two, codons don't encode for proteins but rather components of proteins (amino acids) that the RNA/ribosome "interprets".

These lead to " wobble pairs " which in turn allow a single tRNA to match several different-but-synonymous codons.

On top of that, some codons have a special meaning, such as " ".