Question

To create a knockout mouse, after introducing to embryonic stem (ES) cells a DNA construct in which a specific gene is mutagenized by the insertion of a drug resistance marker, the cells:

Question 2 options:


that have deleted the transgene will grow in the presence of the drug and the nuclei are injected into a host blastocyst.


that have incorporated the transgene by homologous recombination will grow in the presence of the drug and these are injected into a host blastocyst.


that lack the transgene will grow in the presence of the drug and the nuclei are used for nuclear transfer.


that lack the transgene grow in the presence of the drug and these are injected into a host blastocyst.

Answer 1

To create a knockout mouse, embryonic stem (ES) cells that have been modified by the introduction of a DNA construct containing a drug resistance marker and that have undergone homologous recombination are selected to grow in drug presence and injected into a host blastocyst.

Step-by-step explanation:

To create a knockout mouse, a specific gene is mutagenized by introducing a DNA construct into embryonic stem (ES) cells. This construct typically contains a drug resistance marker. Following this, the ES cells that have incorporated the transgene through homologous recombination can grow in the presence of the drug. These genetically modified cells are then selected for injections into a host blastocyst.

The process of selecting these cells involves the use of antibiotic resistance markers. For example, cells might be transformed with a plasmid carrying an ampicillin resistance gene. Since only the cells that have successfully incorporated the plasmid will be resistant to ampicillin, they can be easily identified when they grow on media containing the antibiotic.

This technique is a crucial part of creating model organisms, like knockout mice, that help in understanding gene function and for studying disease mechanisms.