Expert: Dana Krempels, Ph.D. - 9/11/2011

Question
Good day
How does DNA evidence work to idnetify people and how is this possible?
Does DNA differ among the races and can one detect different races with DNA?
Regards,
Sunil Mahabir
Pembroke Pines, Florida

Answer
Dear Sunil,

DNA consists of repeating subunits called nucleotides that differ in one very important aspect:  a base component.  Each nucleotide carries either adenine (A), cytosine (C), guanine (G) or thymine (T).  DNA is also thousands of nucleotides long, and every individual has a different order of these four "letters".  It is the order of the letters in any given gene that provides instructions for both embryo development and for operation of the organism itself.  And because each individual has somewhat different DNA coding, each individual is unique.

By amplifying DNA molecules from a sample of tissue, a researcher can sequence the DNA "letters" and compare them among individuals.  This can also be done with proteins, the translated product of the genes.

As far as telling races apart...that's questionable.  There are more differences between individuals than between races, though a few markers have been found that appear to be different among "races" of humans.  For example, it's now known that European and Asian modern human populations have segments of DNA that are from a related subspecies, Homo sapiens neanderthalensis. This is evidently because the ancestors of those modern humans interbred with Neanderthals they met when they migrated north.

Modern Africans lack these DNA markers because their ancestors stayed in Africa and did not encounter Neanderthals.

But overall, our genomes are not significantly different across races, and as we travel and intermarry, those differences are becoming smaller and smaller.

Hope this helps.

Dana