Solving crimes and mysteries
A large portion of human DNA does not code for
genes (units of DNA that contain instructions for creating proteins).
These non-coding regions nevertheless contain much information useful
for forensic and other human identification applications. Non-coding
regions of DNA contain many of the markers used for identity testing.
- Short tandem repeats
(STRs) are sequences of DNA that are 2-6 base pairs long.
The number of repeats in STR markers is highly variable among
individuals, which makes STRs useful in human identification.
STRs are used to create the genetic profiles that help to identify
criminals, prove paternity and other family relationships, and
identify remains found in a disaster area.
- Mitochondrial DNA (mtDNA) is found in the energy-producing organelles of the cell called
mitochondria. Most of human DNA is found in the nucleus in two
copies (nuclear DNA, which is routinely used for STR typing).
Mitochondrial DNA, on the other hand, is a shorter piece of DNA
found in hundreds or even thousands of copies per cell. Analysis
using mtDNA finds its most use in forensics, when there is very
little sample available.
Non-coding regions in mtDNA, called hypervariable regions,
have significant sequence differences that can be used to differentiate
two unrelated individuals. In contrast, biological relatives
have the exact or very similar sequences at this region. Mitochondrial
DNA is inherited through the mother, and the biological relationship
of two or more individuals may be determined by examining their
mtDNA sequences at the hypervariable regions.
Mitochondrial DNA testing was used to identify the bodies of
the Romanovs found in a burial site in Yekaterinburg, Siberia.
Mitochondrial DNA sequences from a maternal relative, Prince
Philip, matched the DNA extracted from the remains of the Tsarina
and her daughters; mtDNA sequence from the Duke of Fife (a maternal
relative of the Tsar) was used to confirm the identity of the
Tsar’s remains.
-
Y chromosome typing (Y-STR) uses short tandem repeats found on the Y chromosome to trace
the ancestry of males through the paternal line. The Y chromosome
is only passed from father to son, relatively unchanged through
the generations, and thus males related through a paternal line
share the same Y-STR pattern. While Y-STR analysis gives clues
about males’ recent ancestry, another type of markers
called SNPs (pronounced “snips,” single nucleotide
polymorphisms) give clues about deep male ancestry—the
early origins of the different human populations, going back
even up to 100,000 years. Analysis of SNPs combined with Y-STR
typing is used to recreate historical migrations of waves of
populations across the world.
For more information about DNA application in solving crimes and
mysteries, visit DNA Interactive: Applications. |
