Central Dogma of Genetics May Not Apply to Cephalopods
ascienceenthusiast.com
ascienceenthusiast.com
One of the most famous is the alteration of the Proline in the collagen. A big part of collagen is made of Proline, and another big part is made of Hydroxyproline (that is like proline, but one -H is replaced by a -OH). There is no code in the DNA for Hydroxyproline, you use the code for Proline and after the molecule is formed then you use a special enzyme to transform Proline into Hydroxyproline. https://en.wikipedia.org/wiki/Collagen#Amino_acids
Also, tRNA sometimes use weird bases, that are also not encoded directly in the DNA.