For a basic primer on how DNA fingerprinting is performed, please refer to the following video. The repeating regions called VNTRs and STRs are equivalent to microsatellites:
Features that we inherit from our parents are largely governed by the coding regions known as genes, which are found on double-stranded DNA molecules in nearly every one of our cells.
As you can see above, each DNA molecule is coded by four nucleotides–chemical building blocks that are represented by the letters A, T, C, and G. For a stable molecule to form, As must bind with Ts on the opposite chain, and Cs must bind with Gs. This spiraling structure, known as a “double helix,” winds into denser accumulations of DNA and proteins to form chromosomes (the X-shaped structures on top) that are housed within the nucleus (purple region) of each cell. Humans generally have two copies of 23 different chromosomes, for a total of 46, while box turtles have 25 pairs of chromosomes, for a total of 50. When considered as a whole, these chromosomes in humans contain about 3 billion nucleotides altogether, which are paired with their complementary letter (A to T, C to G) along each strand. Turtles, even though they have more chromosomes, have a smaller number of paired nucleotides in total, somewhere in the neighborhood of 1 billion, 200 million letters. This is about the same number of letters in crocodiles and chickens, which are two of the turtles’ closest relatives (along with alligators and dinosaurs, of course).
Now since a complete copy of every chromosome, or the entire DNA code (also known as the genome) can be found in every cell within a turtle’s body–including their red blood cells, which mammals like humans lack–this means that every time that a cell divides, it has to copy every strand of DNA. To give an idea of how difficult a task this might be, we have designed a game that gives you a chance to play the role of DNA polymerase (a.k.a. Poly-D), the specialized protein (or enzyme) that makes DNA replication possible. Give it a try in the space below, and then see your rate of mutation!