 DNA can also be used in paternity testing, and this utilizes short tandem repeat sections of the DNA, where DNA repeats, for example, AC, AG, AC, AG, AC, AG, and so on. And the repeats at each loci are counted, and then that's used in a matrix to determine whether or not someone could be the father of a child. So let's just walk through this example of two alleged fathers, a mother and a child, to determine whether or not one of these fathers is the father and which one it is. The mother at one particular loci has one fragment of 28 repeats and one of 30. The child has 28 and 31. The first father has 29 and 31, and the second alleged father has 28 and 31. So the child could only have received the 28 from its mother because it doesn't have 30, and so either one of the alleged fathers could have contributed the child's 31 repeat gene. So this first locus doesn't rule out either of the alleged fathers. So we look at the second locus. The mother is 9 and 10. The child is 10 and 11. The alleged father 1 is 6 and 10, and alleged father 2 is 11 and 12. The 10 that the child has has to have come from the mother. So this father can't have contributed the 10 that had to have come from the mother because it's the only one of the mother's alleles that the child has. So at this locus, alleged father 1 couldn't have contributed any of the child's genetic material. So we know at this locus we can rule out alleged father 1. Alleged father 2 could have contributed its 11 allele to the child. When we look at this third locus, mother is 14, 15. The child is 14, 16. So the child had to have gotten its 14 allele from its mother, and so we're looking to find out where the 16 allele could have come from. Again, alleged father 1 is ruled out, but alleged father 2 does have a 16 allele and could have contributed that. In the fourth locus, we see the 7 coming from the child's mother, and the 9 could have come from either of these two alleged fathers. But since we've already ruled out alleged father 1, we know now that we're just still in the running with alleged father 2. 14, 16 for the fifth locus, 14, 15 for the child, so 14 had to have come from the mother, and 15 could have come from alleged father 2. So based on these five loci that we've looked at, alleged father 1 was ruled out by several loci, and alleged father 2 matches all of the loci we're looking at. So alleged father 2 could possibly be this child's father. Nowadays, you can get a paternity test at the drugstore for $20, send it off to a lab. $150 later, they'll tell you whether or not you are the father of the child. So paternity testing has become something that can be done at home. Well, not technically at home, you have to send it away to a lab, but it doesn't require a lot of fancy equipment to gather the samples, and so it's becoming something that is an everyday life example of how we can use DNA technology.