AP Biology class blog for discussing current research in Biology

Tag: house mouse

Gene Editing Used to Eliminate Invasive Rodent Species’ on Islands

Species of Invasive House Mice have been not just a nuisance, but potentially dangerous and damaging on islands for hundreds of years. These house mice can be dangerous, as they have the potential to spread diseases by getting into food stores or biting humans, to cause asthma or allergy flare ups, and to bring unwanted insects such as fleas, ticks, or  lice into a home. Scientists have been looking for a way to remove these invasive pests from homes throughout time, and to no avail. Now, they have found a new way to eliminate entire populations of these pests at a time in a mere 25 years. 

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With the emergence of DNA editing technology, scientists have found  a way to edit the mice’ DNA so that a certain chunk of the edited DNA is inherited way more often than the average trait. This lab-created trait is called a gene drive, which had in the past been used to successfully reduce many pesky populations of insects before, but had not been proven effective in mammals. To fix this issue, scientists decided that they most discover more about the haplotypes, which are “naturally occurring group(s) of genes that gets passed on as a unit during replication” within house mice. They discovered that the t-haplotype within house mice get passed on to offspring 95% of the time, instead of the usual percentage of 50%. The editing of this t-haplotype was found to be very favorable. This haplotype evolved naturally within these house mice, meaning that will continue to be present in the wild, and there is no projection of resistance to this haploytpe being found anytime soon. Another reason why the editing of this gene sequence is favorable is that it is only present in the invasive species of house mice, meaning that it will not effect other noninvasive species


Now the only question is, how will scientists change this haplotype? Well, as CRISPR technology is emerging and evolving, it has been found as the obvious tool to use to edit this gene. Molecular Biologists have used CRISPR to edit the mice’ DNA to add the CRISPR tool into the t-haplotype. There are two affects of this change, when male mice with a heterozygous genotype of the edited gene mate, the CRISPR genes inserted will cause any baby female mice created to be infertile. The other effect of this genetic change is that males with the homozygous genotype of the edited gene will be sterile.


Now you might be asking, “has this format gene editing to eliminate the population of the invasive house mice actually been proven effective in any way?” Well, the answer to that is complicated, as scientists have not yet properly tried it out on any island populations. They have used computer simulations to test their hypothesis, finding that in the simulation that after adding 256 mice with the altered gene into the population, the island population of this mouse would go extinct within 25 years. Scientists have still only tested the changing of the t-haplotype within these mice in labs, and have not yet tested the use of CRISPR to effectively damage genes needed for fertility in the house mice. More testing must be done to effectively ensure that this method of eliminating the species is effective, and so we might have to wait some years to begin the overall mission. Overall, scientists are hoping to find a way to eliminate populations of invasive species such as the house mouse in timelines smaller than 25 years,  and many are looking to the future of CRISPR technology as the true way to achieve this goal.

CRISPR: how one tool can change an entire generation (of invasive mice).

In recent years, technology has heavily impacted scientists abilities to change the world. CRISPR is a recently discovered gene editing tool that is revolutionizing the way scientists are treating patients and curing diseases. Recent research has also found that CRISPR can be used to help mice infestations in certain parts of the world (random, but cool)!

CRISPR logoMice infestations are a problem in many islands, and CRISPR is here to help. Scientist believe they had found a way to make an entire mice population extinct (in a few decades) by using gene editing via CRISPR. In order to understand exactly how scientists plan on doing this, it is important to understand what a “haplotype” is. A haplotype is a set of genes that are inherited by the next generation together. The “regular house mouse” has what’s called a “t-haplotype,” and it’s passed down roughly 95% of the time (a lot compared to the normal 50%). The study states that male house mice with two t-haplotype copies become infertile, and females with two t-haplotype copies will become sterile as well. As we know from AP-Biology, when an organism has two copies of some gene, it is known as homozygous- meaning it has two of the same alleles of some gene. In this case the phenotype that makes the mouse homozygous would be the altered t-haplotypes. If a mouse has two of these altered t-haplotype genes, it becomes sterile and cannot reproduce.

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CRISPR plays a crucial role here – by using gene editing through CRISPR technology, scientists are able to edit the t-haplotype of the M. musculus house mouse so that next time a male M. musculus mates with a female, the offspring will become infertile. That’s right, CRIPSR can be used to completely alter and wipe an an entire M. musculus population over the course of a few years. By using computer technology, scientists predict that by adding just 256 “altered” mice to a certain island population of mice, an island of 200,000 mice can be fully wiped out within about 25 years.

Researchers in laboratoryScientists are hopeful, optimistic, and invested in CRISPR technology. The “25 years later” prediction is a long time to wait, and scientists hope that sometime in the future, CRISPR will be able to work faster, allowing problems to be solved more quickly and more efficiently. I think that this study is an important part of CRISPR potential, and it makes me very curious to see what CRISPR has in store for the future, and what other kinds of animal related issues it can help solve.

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