I don't really understand genetics very well, but I know that among the key genetic building blocks for humans are the chromosomes contributed by our parents and that they determine the sex of the child. Two X chromosomes and you're a female, one Y chromosome and one X chromosome and you are a male. So, Y chromosomes only get passed from father to son.
My wife, Kate, has got me interested in genealogy. A growing aspect of the field is genetic genealogy. Companies will sell you a kit containing a swab that you run around the inside of your mouth that you then return to the company for analysis. I find it all mind boggling, but essentially you can determine your maternal lineage with mitochondrial DNA and paternal lineage through your Y chromosome. So, any male or female can determine their maternal lineage, but because only men carry the Y chromosome, a female wanting to determine their paternal lineage would need a male member of a close male relative (e.g. father or brother) to contribute a sample.
This type of testing will allow you to determine your ethnic lineage, which I find quite interesting. More importantly, though, many companies and groups have databases of DNA results that allow you to match up with others who have contributed their results to the database, giving you potential leads for growing your family tree.
How cool is that? This another item I look forward to pursuing in the not-to-distant future.
(I will close with my apologies to biologists and geneticists everywhere for any botching I may have done in my explanations of this topic.)