Why do we have 64 codons

The strand of messenger RNA then floats over to a ribosome , possibly the most amazing enzyme in nature. A ribosome looks at the first codon in a messenger RNA strand, finds the right amino acid for that codon, holds it, then looks at the next codon, finds its correct amino acid, stitches it to the first amino acid, then finds the third codon, and so on.

The ribosome, in other words, reads the codons, converts them to amino acids and stitches the amino acids together to form a long chain. When it gets to the last codon -- the stop codon -- the ribosome releases the chain. The long chain of amino acids is, of course, an enzyme. It folds into its characteristic shape, floats free and begins performing whatever reaction that enzyme performs. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots.

Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Prev NEXT. How can there be 64 codon combinations but only 20 possible amino acids? Ernest Z. Sep 28, Explanation: And you must note that more than one codon may code for the same amino acid.

Three of the codons are stop codons. They do not code for any amino acid. Related questions What are common mistakes students make with anticodons?

Following this discovery, Nirenberg, Philip Leder, and Gobind Khorana identified the rest of the genetic code and fully described each three-letter codon and its corresponding amino acid. There are 64 possible permutations, or combinations, of three-letter nucleotide sequences that can be made from the four nucleotides. Of these 64 codons, 61 represent amino acids, and three are stop signals. Although each codon is specific for only one amino acid or one stop signal , the genetic code is described as degenerate, or redundant, because a single amino acid may be coded for by more than one codon.

It is also important to note that the genetic code does not overlap, meaning that each nucleotide is part of only one codon-a single nucleotide cannot be part of two adjacent codons. Furthermore, the genetic code is nearly universal, with only rare variations reported.