Y-Chromosome STRs
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Y-Chromosome Short Tandem Repeat (STR) Markers

Introduction to STRs

 Tandemly repeated DNA sequences are widespread throughout the human genome and show sufficient variability among individuals in a population that they have become important in several fields including genetic mapping, linkage analysis, and human identity testing.  These tandemly repeated regions of DNA are typically classified into several groups depending on the size of the repeat region.

Minisatellites (variable number of tandem repeats, VNTRs) have core repeats with 9-80 bp, while microsatellites (short tandem repeats, STRs) contain 2-5 bp repeats.  The forensic DNA community has moved primarily towards tetranucleotide repeats, which may be amplified using the polymerase chain reaction (PCR) with greater fidelity than dinucleotide repeats.  The variety of alleles present in a population is such that a high degree of discrimination among individuals in the population may be obtained when multiple STR loci are examined. 

There are literally hundreds of STR systems which have been mapped throughout the human genome.   Several dozen have been investigated for application to human identity testing.

In October 1993, the DNA Commission of the International Society of Forensic Haemogenetics (ISFH) recommended the nomenclature for STR systems which is commonly used today.   Reading the literature and trying to compare results between laboratories around the world may be confusing without understanding this issue.   Some kind of consensus should be reached by the DNA typing community to make comparison of results easier. 

While the use of STRs for genetic mapping and identity testing has become widespread among DNA typing laboratories, there is no single place where information may be found regarding STR systems.  Nonetheless, the “Short Tandem Repeat DNA Internet DataBase”, created by Drs. John M. Butler and Dennis J. Reeder of the National Institute of Standards and Technology (NIST), Biotechnology Division, is an attempt to bring together the abundant literature on the subject in a cohesive fashion to make future work in this field easier.  Check it out at   http://www.cstl.nist.gov/biotech/strbase/ .   More than you can read in a lifetime.