We oftentimes hear about studies saying things like "x gene has been shown to be responsible for y." Like this paper for instance, which found that mutations in the rhodopsin gene can affect vision in mice. That's awesome and cool but how exactly do we go about connecting those two things? Well, turns out there are lots of ways, all of which depends on what exactly you are trying to find out.
The first method is called a "forward genetic screen." This is basically when you start out knowing what phenotype (the individual characteristic) you want to examine and are trying to find what genes are responsible for it. This involves making random mutations in your test subject, seeing what characteristics changed, and then going back and seeing what specific genes caused that change. One way of inducing mutations is through chemicals that introduce stop codons into an organism's DNA in random locations which can modify a gene's function. Another technique involves exploiting RNA interference in which you can introduce specific enzymes that degrade mRNA and destroy any instructions needed to build certain proteins, thus also affecting the phenotype.
Steps for forward genetic screenings
The second method is called a "reverse genetic screen." This is when you are trying to find the function of a gene by connecting it to a specific phenotype. Similar techniques are used to disrupt DNA function, only this time they are not random.
A couple of handy guides!
It is important to note that often times it is not a single gene but a network of genes that is responsible for a phenotype, thus making this more complicated. I've only scratched the surface regarding methods and technologies that can be used to determine gene functions. As always, reading about this stuff makes me thankful we live in an era in which analyzing genes is easier than ever.
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