In genetics, most authors say/write "gene G codes for protein P", while some say "gene G codes protein P". German being my mother language, the first form looks a little strange to me, since also in German now it's very common to say "Gen G kodiert für Protein P", which is wrong in German. With my German background, "to code" ("kodieren") can be used transitively with meanings:

  • to encode: X codes Y means X creates the code of Y, e.g. "The text editor codes the character 'A' with the ASCII-Code to the number 65".
  • being the code of something: X codes Y means X is the encoded form of Y, e.g. "The number 65 codes the letter 'A'"

In most cases it is clear by the situation or fact whether X is the encoder or the code of Y.

So are there any (general) examples of using "code for" when meaning "is the code of" beside genetics? Would you say "The number 65 codes for 'A'"?

  • The number 65 decodes to ’A’. The number 65 is the code for ’A’. ’A’ encodes to 65. A’s code is 65. I code for work and sometimes for fun. – Jim Oct 29 '17 at 19:40
  • Welcome to English Language & Usage. – J. Taylor Oct 29 '17 at 19:55
  • @Jim Thanks for the prompt answer! But: Where is "X codes for Y" in non-genetic language? – Udo Bellack Oct 29 '17 at 20:21
  • I'm just watching a video of Jennifer Doudna, who should have some experience in genetics :-) She says "Gene encodes Protein", see (youtu.be/SuAxDVBt7kQ?t=254) – Udo Bellack Oct 29 '17 at 21:17
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    I don't think the phrase is used much this way outside genetics. – Barmar Oct 30 '17 at 15:14

The answer would be in the scientific literature because this is a scientific usage. I assume that because the development of the genetic code occurred in the early 1960s and was partly carried out in the USA, the use of "code" as a verb and the somewhat colloquial expression "codes for" would have been more common than the (more proper) "encodes". Reviewers in the USA would generally not have a problem with "codes for" even in a formal scientific paper or a textbook. Nonetheless, to say that "Gene X encodes protein Y" is not only correct but preferable, in my view. This is because the information for protein Y is "contained within" the gene.


Keep in mind that genetic code, unlike ASCII code, is not a one to one code.

For example, GGG, GGA, GGC, and GGT all correspond to Glycine. For a protein with n amino acids, there wound be on the order of roughly 3^n different possible DNA or RNA sequences that code for the exact same protein.

Also, there is a standard of using the word "transcribe" when going from DNA to RNA and "translate" when going from RNA to protein.

On the other hand, ASCII code and Morse code are one to one codes.

If you what to say something different you could say for Morse code:

an E is represented by just a single dot, and a T is encoded as a single dash.


The reason geneticists may use the word 'for' comes down to the entity that they're talking about.

The gene is represented by a physical combination of amino acids in a DNA/RNA string, and it contains the information associated with the structure of the protein, another physical object.

It's common enough to hear descriptions of objects or people doing things for other objects or people. For example: "Jimmy was able to bat, but he couldn't run. Thankfully, Sarah offered to run for him." An example with objects would be: "I need more bullets for this rifle."

On the other hand, an abstract entity like a letter or a number is not typically thought of in the same way. This is why it may seem weird to you that a gene can encode for a protein. You are thinking of the gene and protein in terms of their underlying information, not as physical structures.

You wouldn't see the use of for as commonly when talking about ASCII encoding, because nobody is thinking about the physical underpinning, namely the CPU of the machine. But you could say: "The CPU and computer screen decode binary information for the reader." You may still be describing the conversion of an integer to a character, but you're casting it in terms of the physical objects, not the underlying information. All of a sudden, for is home again.

To give a specific example of the use of "code for," we just need to make people or objects the object of the sentence:

"I code for the fun of it."

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