Explain the biological theory underlying DNA testing and how such evidence is usually presented in court

Question

What will be an ideal response?

Answer 1

The human body consists of billions of cells, most of which carry chromosomal DNA. Human genetic information is encoded in the DNA found in chromosomes. The DNA in chromosomes is arranged in a sequence of paired organic bases, called base pairs, which form the well-known twisted double-helix DNA chain. A set of chromosomes (one from the mother, one from the father) might contain 3 billion of these base pairs arranged in sequences on the DNA chain. Knowledge about these sequences in chromosomes makes DNA matching possible. If we compare DNA chains from two people who are not identical twins, we discover two things. First, the chains, or sequences of base pairs, are identical or more than 99 percent of the base pairs. Humans are, after all, more alike than different. Second, at certain identifiable sites, called locus points, base pairs vary from one individual to another. At such a locus, for example, where eye color is determined, base pairs join in a sequence that is repeated; measuring the size of a repetitive sequence of base pairs at many such locations gives a fingerprint-like picture of the DNA chain, since at these locations the sequence of base pairs varies among different individuals. Thus, like fingerprints, if we have a picture of enough of these locations where human DNA varies, then we have an individual's genetic fingerprint. Experts who perform DNA tests and later testify to test results and meanings usually give probability estimates, taking into account different population samples.