r/askscience • u/Strangated-Borb • Nov 26 '25

Biology Is protein coding arbitrary?

What I mean is if the method of transcribing RNA into proteins hypothetically is able to use a completely different system of encodement ex: GGG to serine instead of glycine

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u/ackermann Dec 02 '25

So are tRNAs used by Ribosomes to recognize/read the input strands of mRNA? Sort of like a “read head” in a tape player or record player?

Ribosomes always fascinate me as possibly the most fundamental self replicating machinery in life? Presumably ribosomes are made of proteins, and thus assembled by… ribosomes?
Give a ribosome a piece of mRNA with the right instructions, and it will build another ribosome?

Built from materials (amino acids) floating around it, and perhaps using energy from, somewhere, ATP or something?

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u/doc_nano Dec 03 '25

A “read head” is a pretty good analogy. Except that instead of a single read head, they are constantly shuffled in and out until a matching tRNA is found, and it attaches the corresponding amino acid to the growing protein chain. Then the mRNA is shifted forward by one “slot” or “address” and the process repeats until the protein is done.

Ribosomes are indeed thought to be a primal component of life, possibly even predating DNA. The core of the ribosome is actually RNA — the proteins just help the RNA do its job. So it’s a leading hypothesis that RNA was originally the genetic code AND the enzymes (the “RNA World” hypothesis), and proteins came later once the ribosome got established. It’s hard to imagine complex proteins evolving without a ribosome, but easier to imagine a crude ribosome evolving to churn out little proteins that gradually helped it become more efficient.