I am working on an experiment involving the analysis of expression of a protein X in wild-type (+/+) and knockout mice (-/-). In the knockout mice, the gene of interest has been constitutively knocked out. For both genotypes, I am analysing postnatal day 2 (P2) and postnatal day 10 (P10) mice.

If in the knockout P2 and P10 mice, the levels of protein X are significantly increased compared to the wild-type P2 and P10 mice respectively, one could say that this effect could possibly be due to the gene of interest being knocked out. However, I was wondering, is 'constitutive effect' the proper terminology to explain a biological effect that occurs due to a gene being constitutively knocked out?

Any insights are appreciated.

  • $\begingroup$ "...one could say that this effect could possibly be due to the gene of interest being knocked out." Assuming the wildtype and knockout mice share a common genetic background and appropriate controls are performed, you should be able to say this with more confidence than "possibly." $\endgroup$
    – MikeyC
    Jul 8, 2021 at 14:58
  • $\begingroup$ Not necessarily... knockouts are a rather crude and problematic tool for studying regulatory systems. Have you read "Can a biologist fix a radio?" $\endgroup$
    – jakebeal
    Jul 8, 2021 at 15:11

1 Answer 1


I have generally seen the term "constitutive" used to refer to a "always on" expression of a gene with no anticipated regulatory interaction. Thus the term "constitutive knockout" seems a little bit oxymoronic to me, and I would tend to prefer a different term, like simply "knockout" or, if you really need to differentiate from conditional knockout, "unconditional knockout."

Likewise, if you wrote "constitutive effect", I would tend to interpret that as an effect of a gene being on, not a gene being knocked out. And even then I would find the terminology unsatisfying, as again it's mixing ideas of regulation (effect) and non-regulation (constitutive).

I would suggest you keep the terminology more direct and simply refer to the knockout itself, e.g., "knockout effect", or "effect seen in knockout mice".


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