Been listening lot of EWU and general crime documentaries/podcasts on my daily commute, and I keep hearing about DNA profiles. After looking it up briefly, I saw that our DNA is all so similar anyway, but there are specific identifiable patterns. Someone can match the profile but not be an exact match- how does this work? What are traits that a DNA profile can describe?
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It’s single-nucleotide polymorphism typing. That’s to say, known places in the genome where a single “letter” (nucleotide, A/T/C/G) of DNA is sometimes different from how it is in the vast majority of humans. This tells you essentially nothing about a person’s traits, outward appearance and such, but can be used to test their relatedness to other people or to samples of unknown origin (such as from a crime scene).
Imagine a big book. Every human has a copy of this book, which they get by manually copying over from their parents’ books. Very rarely, people make a random typo, which they can’t correct and their children will go on to blindly copy that typo when it’s their turn to write out the book. You will end up with typos that are distinct to your family line; maybe in yours, a single instance of “car” got turned into “cat” on page 178. The vast majority of other humans on the planet still have “car” there. If you find the “cat” typo in a given person, it gives you a clue about their ancestry, and thereby their identity. If there were a couple hundred of these characteristic typos, you could look for all of them in a person’s book to assemble a profile of exactly which ones they do and don’t have. That’s more or less how SNP typing works.
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