Question

Knockout mice are usually created by:

• A. chemically mutagenizing a mouse and selecting for mutant offspring.
• B. creating a chimera by fusing cells from two different cell lines.
• C. infecting the mouse with a retrovirus.
• D. transfecting embryonic stem cells with an inactivated gene.

Hint:

Knockout = ES Cells + Homologous Recombination.

Answer 1

The Correct Option is D

Step 1: Concept
Gene knockout technology involves the targeted disruption of a specific gene to study its function in vivo.

Step 2: Meaning
A "knockout" means the gene is made completely non-functional.

Step 3: Analysis
The standard procedure involves taking Embryonic Stem (ES) cells and introducing a DNA construct containing an inactive version of the target gene. Through homologous recombination, the inactive gene replaces the functional one in some cells. These modified ES cells are then injected into a blastocyst to create chimeric mice, which eventually produce pure knockout offspring.

Step 4: Conclusion
The core step is the transfection of ES cells with an inactivated gene construct. Final Answer: (D)