The Need for Standardized Y-STR Terminology

Public release date: 23-Dec-2008

Contact: Michael E. Newman
michael.newman@nist.gov
301-975-3025
National Institute of Standards and Technology (NIST)

NIST guides genetic genealogy labs toward improved accuracy
Anyone who has watched crime dramas on TV knows that forensic scientists can use DNA “profiling” to identify people from evidence gathered at a crime scene, establish a paternity link or help free an innocent person who has been wrongly jailed.    A lesser known but rapidly growing application of DNA profiling is tracing a person’s paternal ancestry — a process known as genetic genealogy.    The laboratories performing this testing often differ in their results, making data comparison between labs difficult and casting doubt on reported genetic matches.    Researchers at the National Institute of Standards and Technology (NIST) recently published a paper* with recommendations for genealogy testing that they hope will improve the accuracy and reliability of the product.

A man’s paternal lineage can be traced using the DNA on his Y chromosome (Y-DNA), which, like many European surnames, passes from father to son.    DNA profiling provides a genetic path that follows the surname through the years.    Women who wish to know their ancestry can ask their father, brother, paternal uncle or paternal grandfather to take the test for them.

Genetic genealogy works by studying the sequences of repeating nucleotide (the base components of DNA) patterns on the Y chromosome known as short tandem repeats (STRs).    Each STR is considered a separate marker for potential genetic matching because the number of times it is repeated will be the same for related males.    For example, a person may have one STR sequence that repeats 12 times, another 11 times, a third 17 times and so on.    If another male has a Y chromosome with a high percentage of the same STRs, it is considered likely that they share a common ancestor.    Accurately counting the number of repeats is a tricky task and the source of much of the error in genetic genealogy tests, causing genealogists to make incorrect matches or miss family connections altogether.

In their paper, the NIST researchers explain the basis for the differing interpretations and recommend a solution using the agency’s certified reference material for human Y-chromosome DNA profiling (Standard Reference Material 2395), a collection of Y-STR markers that can serve as a means for genetic labs to calibrate their testing equipment.    The researchers “strongly encourage [SRM 2395’s] use to enable compatible and calibrated measurements to be made between different Y-STR testing laboratories.”

Their sentiment is echoed by an editorial in the Journal of Genetic Genealogy that says of the NIST paper, “The advantages of having industry-wide standards are compelling for both buyers and sellers of genetic genealogy services.”

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* J.M. Butler, M.C. Kline and A.E. Decker. Addressing Y-chromosome short tandem repeat (Y-STR) allele nomenclature. J. Genetic Genealogy 4:125-148 (2008).