Business · Ars Technica
Researchers try to cut the genetic code from 20 to 19 amino acids
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The genetic code is central to life.
Key facts
- Replacing 20 of the 21 genes and leaving rplW untouched led to cells that not only survived, but grew at about 70 percent the rate of an unmodified E. coli cell
- The cells were grown for 400 generations and typically picked up 20–30 mutations, but none of those restored an isoleucine to any of the ribosomal proteins
- Eighteen of those worked with no obvious problems, another 19 grew more slowly, and the changes were lethal for the remaining 13 genes
- Iterative testing using four different software packages produced alternative protein sequences for 25 of these 32 proteins that eliminated the fitness issues
Summary
Most hypotheses suggest that earlier forms of life had partial genetic codes and used fewer than 20 amino acids. First off, why would you do this? The reasoning here seems to be that, before the last common ancestor of life on Earth, organisms experimented with various genetic codes and probably used a mix of proteins and catalytic RNAs to run their metabolisms. Isoleucine is one of three highly similar amino acids, along with leucine and valine.