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turquoise_amethyst t1_iw3o3ym wrote

Reply to comment by Chiperoni in How do medical researchers obtain lab animals with diseases like specific forms of cancer which arise spontaneously? Do they raise thousands of apes and hope some eventually develop the disease? by userbrn1

How is a colony maintained if the specific mutation causes infertility? Do they have to start from scratch every time?

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ChemicalBliss t1_iw3s79v wrote

If it’s recessive, they can breed 2 mice that are heterozygous for the mutation and screen the pups for having 2 copies of the mutation.

Edit: if it’s dominant they can use a conditional system where the gene only gets turned on in the presence of a drug (such as tetracycline), or the gene is turned on in a tissue specific manner.

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mattc286 t1_iw4c359 wrote

To further expound, it depends on what "kind" of infertility. If the dams can produce fertile eggs but the embryos can't implant or there's a placental defect, you can harvest the eggs, do IVF, and implant in another dam. If the males make sperm but have vascular issues that make them impotent, you can treat with drugs (like Viagra) or harvest sperm for insemination/IVF. If the mice can't produce gametes, you can use "conditional knockout" like the Cre/LoxP system so the gene is present and working until you're ready to make the test animals, and then either knockout the gene in the whole animal or in the specific tissue you want. I've also seen temporary "rescue" of a knocked out gene with injecting mRNA at the time of fertility defect to overcome the issue long enough to get viable pups.

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