5.1
Scientists can inactivate or knock out a gene in animals, commonly mice, to learn more about the function of the gene, usually by replacing it with a targeting vector, an engineered piece of DNA.
The targeting vector has sequences that are homologous, identical to the sequences before and after the gene. It usually also has a positive selection marker such as the gene for neomycin resistance NeoR in the middle and a negative selection marker like the gene for thymidine kinase TK at one end.
When introduced into embryonic stem cells it replaces the gene through homologous recombination which occurs naturally between stretches of DNA with similar sequences. Cells where the gene has been correctly replaced will contain the positive marker but not the negative one allowing them to be identified in culture. These cells are then inserted into a mouse embryo and implanted into the uterus of a female. The resulting mouse has a combination of normal cells and cells with the gene knocked out on one chromosome.
These mice are then bred to generate so-called knockout mice that are homozygous for the knockout in all cells.
Aby dowiedzieć się więcej na temat funkcji genu, badacze mogą obserwować, co się dzieje, gdy gen zostanie inaktywowany lub ”znokautowany”, tworząc gen…
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