[thedoc (OP)]

Melndlovu asked the Naked Scientists:
   
What is used to determine a DNA test for a dead person to acomplish their relationship with the living people?

What do you think?

[evan_au]

An early method for DNA matching was to focus on particular segments of DNA which differ in the number of DNA repetitions within the population. There are many such "variable number tandem repeats" scattered throughout our DNA. Depending on the length of this region in an individual, the sample of DNA will migrate a different distance through a gel.

Since we have 2 copies of each chromosome, this usually produces 2 marks for each of these VNTRs (one from mother, and another from father; sometimes both may happen to be the same length, producing just 1 mark).

Our siblings have also inherited their genes from the same parents (but not necessarily the same ones), and our children inherit their genes from us.

So if we can get a DNA sample from a body, and also from close relatives of a missing person such as their parents, siblings and/or children, it is possible to compare the marks from each person to determine the probability that they they are related (eg parent/child, brother/sister, cousin, etc).

Testing the DNA from a crime scene can be a bit simpler, because we are looking for an exact match, rather than the probability of a match (but sometimes DNA from a crime scene turns up an inexact match which points to a close relative of the perpetrator).

Reading DNA is getting easier every year, and so we can expect more sophisticated methods to become feasible in the next few years.

See: http://en.wikipedia.org/wiki/DNA_profiling