DNA is a complex molecule found in the nucleus of most cells in the human body. Nuclear DNA is found in 23 pairs of chromosomes, and is inherited from both parents -- with the sole exception of Y chromosome DNA from the 23rd pair. Y chromosome DNA is only inherited by males from their father.

Y-chromosome DNA consists of a long string of over 50,000,000 chemical bases, each of which is designated C, A, T, or G. Patterns of bases (e.g. GATA) sometimes repeat themselves on the Y-chromosome. These repeats are called STRs (Short Tandem Repeats), and occur at known "marker" locations on the DNA molecule.

STRs at marker locations can be counted, and become the values assigned on typical Y-DNA test reports. These marker values are passed down relatively unchanged from father to son.

Mutations: Occasionally, the number of repeats changes from generation to generation. These changes are called "mutations", and accumulate at an average rate of about one every 300 generations.

TMRCA: By looking at the differences in mutations between two or more males, we get a general idea of their Time to a Most Recent Common Ancestor (TMRCA). A low TMRCA indicates a close or distant cousin.

Results that are grouped together by common color background in the Little DNA project have a TMRCA of 700 years or less (or about the time hereditary surnames have been used in Europe).

Haplogroups (HG): Marker values are also used to define "haplogroups", which help trace the migrations of mankind across time and across continents. Males with the same haplotype share a common "deep ancestry" in the last thousands of years, but only share a recent ancestor if their results are similar.

Please see Presentation for a DNA Presentation.   Please see Contexto for more technical info on DNA.

Please see Family Facts for facts and maps pertaining to our families, and see Links for more DNA websites.