A Comparison of DNA Testing Results

for the families of

Michael Joseph Lalley

and

John Lally of County Galway

The table below shows results of initial DNA testing on a very limited basis. It includes too few samples for a conclusive result, but the six-step genetic mismatch gives every indication that the families of Michael Joseph Lalley and John Lally are unrelated, although they share variations of the same surname.  This great a distance among the 12 DYS markers suggests a divergence of the two lines at least 60 generations in the past.

DYS Numbers

Earliest Ancestor of Record	Hg *	393	390	19	391	385 a	385 b	426	439	389-1	389-2	392	389
Michael J. Lalley, b. ca 1850	R1b	13	24	14	11	11	13	12	12	12	13	14	29
Perhaps Co. Roscommon
John Lally, b. ca 1800 - 1815	R1b	13	24	15	11	11	16	12	12	14	14	13	30
Headford Vicinity, Co. Galway

Hg* = Haplogroup, a population group of lines that are related through a single paternal or maternal ancestor. R1b is a paternal haplogroup, since it is determined from the Y-chromosome found only in males.

DYS 19 is also known as DYS 394.

The differences at DYS 389-1 and DYS 389-2, which are overlapping markers, count as only a single mutation, because it took place in the region common to both markers. Additional mutations are counted only when the difference between the values at the two markers also varies between samples, indicating that one or more additional changes took place beyond the region shared by both markers.

The DYS numbers identify short tandem repeat (STR) genetic markers on the DNA strand. Each consists of a three-, four- or five-base sequence, repeated the number of times shown in the table. Changes occur randomly and infrequently, at an average rate of one mutation per marker every 250 to 500 generations, so that in comparing 12-marker samples from known related individuals, we should expect on average that one of the 12 will change every 20 to 40 generations. 

It has become obvious from observation of thousands of samples that some markers change or mutate at a faster rate than others. While a study of actual 'faster rates' of individual markers has been completed, results are still being prepared for publication.

The markers in red have shown a faster mutation rate then the average, and therefore these markers are very helpful at splitting lineages into sub sets, or branches, within a family tree.

Explained another way, if two samples match on all of the markers except for one or a few of the ones that mutate more quickly, then this mismatch only slightly decreases the probability that two people with the same surname who match 11/12 or even 23/25 share a recent common ancestor.