Bacteria and humans read codons the same way
- The idea
- Predict
- See it
- Why
- Check
The idea
“Each organism has its own genetic code, so a codon can mean one amino acid in us and another in bacteria.”
When a human gene fails in bacteria, it's tempting to blame a different code. Nearly all life shares the same one.
The short version
The mistake: Each organism has its own genetic code, so a codon can mean one amino acid in us and another in bacteria.
What's actually true: The genetic code is nearly universal. Bacteria, plants, fungi and animals read each codon the same way.
- A codon is three mRNA bases. The tRNA that pairs with it brings one amino acid. Of the 64 codons, 61 code for amino acids and three mean stop.
- Bacteria, plants, fungi and animals all use the same codon table. The few exceptions, such as in mitochondria, change only a handful of codons.
- So bacteria given DNA for human insulin make the same insulin we do. When a moved gene fails, look for introns bacteria can't remove or sugars they can't attach.
- The shared code is strong evidence of common ancestry. Changing a codon's meaning would change every protein that uses it, so the table has barely changed.
On the exam: A codon means the same amino acid in almost every organism.