Gene knockoutSpec D1.3.8
In short
Gene knockout is a technique for investigating the function of a gene by changing it to make it inoperative. Researchers compare the knockout organism with a normal one; any difference in phenotype suggests what the gene does. Libraries of knockout organisms, each lacking a different working gene, exist for some model species such as mice and yeast.
Gene knockout is a technique for investigating the function of a gene by changing it to make it inoperative. The gene's base sequence is altered, or part of it removed, so that no functional product is made.
- Choose a gene whose function is unknown.
- Make the gene inoperative in an organism (a knockout organism).
- Compare the phenotype of the knockout organism with that of a normal (wild-type) organism.
- Any difference, such as in development, behaviour or metabolism, suggests what the gene normally does.
Details of knockout techniques are not required. Students should know that libraries of knockout organisms are available for some species used as models in research. For example, collections of yeast strains exist with nearly every gene knocked out one at a time, and international projects are building a knockout mouse for each mouse gene. Researchers can obtain an organism with a particular gene knocked out instead of making it themselves.
A knockout experiment needs a control: wild-type organisms of the same strain, raised in the same conditions, so that any difference can be attributed to the missing gene.
Written and checked against the IB Biology HL specification · Updated October 2026