Why use MICE?
Out of an entire world of animals, many people wonder, why use mice? Well, there are a few reasons behind this practice, principally genetic and scientific, however there are some other factors that are considered.
Convenience: In terms of general logic, mice are cheap to raise and feed, and small enough to handle comfortably in a lab.
Life Span: Mice also have a pretty short lifespan between generations, so they reproduce and die faster than us, (One mouse year feels like 30 human years). This allows scientists to observe the effects of different tests/studies on offspring in a short amount of time.
Genetic Match-up: Mice have a close analogous genetic and physiological match to humans. This means that many DNA elements are the same in both mice and humans. By 'deleting' specific genes in mice, scientists can get an idea of how those certain genes work in humans as well. Surprisingly enough, 99% of human genes have counterparts in the mouse, and 81% have identical, one to one counterparts (see image G1 below).
The mouse was one of the first mammals, besides humans, whose genome was fully sequenced. The reason why we share so many genes with our furry relatives is that mice, humans, and many other mammals, all descended from a common ancestor about the size of a small rat 75 to 125 million years ago...although we don't look much like mice anymore! This similarity is important, because even in the process of comparing the mice and human genomes, researchers discovered 1200 new human genes. Later on, they discovered that 90% of the genes associated with disease and disease symptoms in humans are identical in mice! (see image G2). We have a lot in common with these pesky rodents! Of course, there are some differences.
For instance, the mouse genome is roughly 14% smaller than the human one, and mice have WAY larger litters. The genes for scent are also far more developed in mice. Even so, 40% of the two genomes are directly aligned.
When the mouse is used in science, it is called a MODEL ORGANISM. Scientists use model organisms to study complex diseases involving the interaction of multiple genes, a focal point of biomedical research, and drug efficacy testing. Also, many of the genes responsible for complex diseases such as atherascelerosis and hypertension are shared between mice and humans, meaning that research in mice is very important in the identification of genetic risk factors in the human population.
Oftentimes, naturally occurring, spontaneous genetic mutations will cause afflictions in mice that mimic similar human genetic diseases, another similarity that we share.
In addition, our ability to directly manipulate the mouse genome provides a very powerful tool to model specific diseases for which the causative gene is known. For example, the manipulation of a causative gene that causes cancer has allowed for the creation of hundreds of mouse models of cancer, greatly increasing our chances for finding a cure, with so many test patients.
Scientists can also repress certain genes in mice that have counterparts in humans, to discover which human genes are actually important to perform vital functions.
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As you can see, Genetics play a huge part in the use of mice in laboratories, especially so in various experiments.