But being as how we were performing one in our lab, the same lab where presentations are still being done on Kodachromes, our wet preps are sealed with gaudy nail polish, and the lack of hygienic foot stools switches on the sinks, I knew it couldn't be that complicated.
The process is an extension of a gel electrophoresis technique. DNA is taken from the prospective fathers, the mother, and the child, and then mixed with restriction endonucleases, which cut the DNA at specific recognition points.
Now, DNA is unique to every single person in the world. However, the more closely related you are to a person, the more closely your DNA will resemble that other person's. Variation in DNA is based on amino acid variation, therefore an analysis of the sequence of amino acid and its similarity will yield the relatedness of two different people.
Back to those restriction endonucleases. Since they cut at specific recognition sites (specific sequences of specific amino acids), the cuts will vary depending on the DNA. DNA that closely resembles another person's DNA will have cuts that are very similar, and oftentimes the same exact cuts (multiple digestions with multiple restriction enzymes will yield more specific results). So what does this have to do with child support?
After the gel is run and the fragments allowed to seperate, ethidium bromide is applied to bind to the DNA and mark it. Then the bands of DNA can be visualized under UV light.
The bands are then compared to each other. If the prospective father contributes bands to the child that the mother does not, then that guy is the dad. Probably.
Of course, definite decisions are not made until the process has been repeated with multiple restriction endonucleases multiple times. And then, well, hopefully one of the men is the father.
