What is a knockout gene technique and how is it used in research?

• A. Inserting extra copies of a gene to boost expression.
• B. Inactivating a gene to study function by observing resulting phenotypic changes.
• C. Sequencing a gene to identify mutations.
• D. Using PCR to amplify a gene segment.

Answer: (B)

The knockout approach works by turning off a gene to see what goes wrong, so researchers can infer what that gene normally does. By disabling the gene’s coding region or key regulatory parts, the organism or cells can’t produce the functional protein, and scientists then look for changes in appearance, development, physiology, or behavior. Comparing a knockout with a normal, unmodified organism reveals the gene’s role.

In practice, this can be done by deleting the gene through precise genome editing. Traditional methods used targeted changes in embryonic stem cells to create knockout animals, while modern techniques like CRISPR/Cas9 can introduce mutations that disrupt the gene quickly and efficiently. Some knockouts are designed to be tissue-specific or inducible, so the gene is disabled only in certain tissues or at particular times, which helps when a global knockout would be lethal or confound results.

This is different from boosting gene expression by adding extra copies, which would reveal effects of overactivity rather than loss of function, or from sequencing a gene to find mutations or using PCR to amplify DNA, which don’t directly test a gene’s function.