YDNA. The DYS464 polymorphic marker

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Contents 1 Related 2 Notes 3 Discussion	This is one of a series of articles on Genealogical Methods, prepared in association with The Tapestry. See Index for a list of related articles.

Related

Butler and Schoske 2004 International Congress Series 1261 (2004) 278 – 280, Forensic value of the multicopy Y-STR marker DYS464

Notes

From Steven Bird on Rootsweb Genealogy DNA mailing list, August 2009 citing "FtDNA's explanation from the GAP (Group Administrator Page) on their own website":

DYS 464 was discovered at the University of Arizona by Dr. Alan Redd. This highly volatile (fast mutating) marker is included in the panel to help show changes even within family groups that are closely related. DYS 464 is replicated 4 times in 98.5% of people from Europe and the Middle East (the balance having 5 or 6 copies). Because the marker’s location on the Y-Chromosome is not determinable we sort the marker from smallest to largest (385a/b is treated the same way), and therefore it is possible to overstate or understate the actual genetic distance when making a comparison by eye. Markers 464a-d are copies found at different locations on the Y chromosome. In about 1.5% of the test subjects, more than 4 copies will be present, representing Markers 464e, 464f, 464g.

From Butler and Shoske, 2004:

Abstract. The tetranucleotide Y-chromosome short tandem repeat (Y-STR) marker, DYS464, first reported by Redd et al. [Forensic Sci. Int. 130 (2002) 97] appears to be the most polymorphic Y-STR marker discovered to date. A single primer pair can generate up to four distinct peaks over an allele range of 9 – 20 repeats. Allele calls can be made based on peaks that are present (conservative approach; C-type) or a combination of alleles and peak height ratios (expanded typing method; E-type). We have observed 113 C-types and 179 E-types in 679 males from three US populations.

Discussion

DYS464 is one of the markers commonly used in YDNA testing for genealogical purposes. The marker is "polymorphic" meaning that it exists in "many forms" in a YDNA test sample. In European populations (and some others) variants (A, B, C, and D) are all found in most males. In about 1.5% of the population other markers are also found (E, F, and G). The data are routinely reported as DYS464a, DYS464b, etc. The data for these markers are routinely ordered from smallest to largest (reading left to right). When comparing test results from two different men, there is no practical way to directly compare how each of these polymorphic markers compare with each other.

Suppose that a common ancestor of the two men happened to show the following YDNA pattern

Suppose that the "DYS464c=13" marker showed a mutation that reduced its value to 12 in one of the men, and increased to 15 in the other man. Based on the multistep model, the genetic distance between the two men would be 1+2=3. The results would be displayed as:

As it happens, the second table would accurately describe the genetic distance between the two men as 2+1=3, though some might have difficulty with interpreting the order of the markers. However, this would not always be the case. If, for example, the "DYS464c=13" marker of the ancestor were to change to increase by three steps, then the correct genetic distance would now by 1+3=4,

Yet the display would not show this

which would give a genetic disstance of 2+1=3.

The reason for such discrepancies is that the order of presentation is arbitrary, arranged from smallest to largest values. Unlike non-polymorphic markers, there is no set correspondence between the tested marker form, and the display. The value for any particular form could appear anywhere within the series, depending on how much it changed, up or down.

This makes interpreting the genetic distance for any given comparison rather difficult if it involves DYS464. It is quite easy to over or underestimate the genetic distance under these circumstances.