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In lac operon the 3 structural genes lacz, lacy and laca must have some reason behind their names. While lac refers to lactose but what does z, y and a refer to?

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    I’m voting to close this question because it is a question about the history of biology rather than a mechanism or process. – tyersome Mar 26 '21 at 05:36
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    I think you'll have great difficulty finding the answer to this question, unless you can find interviews with or historical accounts by Jacob and Monod (probably in French) in which they mention this essentially trivial point. – David Mar 26 '21 at 10:25
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    @Tyersome, I believe we can only discover new things if we better understand the history of something. You can't name any gene randomly, selecting any of the 26 alphabets. There must be some reason behind their names. We ought to find that. –  Mar 26 '21 at 10:56
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    @Tyersome, I approached this site with the hope that my questions though not so interesting and just out of mere curiosity would be answered in the most appropriate way. Anyway, I definitely will take your advice, and hope to get it done soon. –  Mar 27 '21 at 10:00

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The Jacob and Monod article on regulation is paywalled, but there do seem to be some PDFs floating around.

In this article, the terminology of z and y is introduced as designators for mutants (z+ and z-, y+ and y-).

  • The z appears to be linked to a term from a kinetic equation.
  • The y is not justified, implying that it is an arbitrarily chosen variable, and such choices are often by convention adjacent to the justified variable (e.g., the index variable i is often followed by additional indices j and then k).

The a component is not present in the original article, but its name seems likely to come as an abbreviation of its function as an acetyltransferase

jakebeal
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    The paper you cite is the original one describing the regulation of the structural lac genes, but it is not the original one describing these genes. You would have to go further back to find that. I am most sceptical that a geneticist would name a gene from a kinetic equation. What evidence do you have to support this? I would imagine y and z are just convenient letters of the alphabet, with a (for acetyltransferase) added later because they had got to the end of the alphabet. But I don't know. – David Apr 11 '21 at 14:37
  • @David In the paper, z is introduced early on as a term for enzyme activity, then later the presence of galactosidase is given as the z+ phenotype, which then links to the lacZ gene. In the section for the phenotypic terminology is introduced, I don't see any citation for the terminology, leading me to conclude that the terminology is being introduced in this paper. – jakebeal Apr 11 '21 at 16:17
  • I used to know geneticists that would know the answer. I may try to trawl back through the literature but it can be difficult. All those old French journals will have been absorbed into something else and probably not digitized. – David Apr 11 '21 at 17:02
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    @David If you find anything better, please do share! – jakebeal Apr 11 '21 at 17:27