1.1 DNA testing can be performed to match other specific people and to identify general backgrounds. Paternal lines are tested by Y-DNA and maternal lines by mtDNA.

In Y-DNA between 10 and 67 markers are tested. A Y-DNA haplotype is derived from the markers. Haplogroups are large groups of haplotypes defining a genetic population.

http://www.ysearch.org/ has a database of 20,000 plus Unique Haplotypes from 28,000 plus records.

The choice on how many markers to test is discussed at

http://www.ftdna.com/faq2.html

It depends on the goals of closeness of matching a common ancestor.

mtDNA tests are based on HVR1 and HVR2 results.

http://www.mitosearch.org/ has a database of mtDNA results.

More DNA testing information can be found at

Family Tree DNA DNA101 with list of Tutorial Links

Also see http://en.wikipedia.org/wiki/Genealogical_DNA_test

There is a collection of Genealogy using DNA bookmarks at at http://del.icio.us/gendna. It is open for anyone to add or edit.