Can a DNA test solve my brick wall?

QMy 3x great grandfather, James Harpley, died on 28 July 1844 aged 56 at Wisbech St Mary, Cambridgeshire. In the 1841 census, he is in Cambridgeshire but states he is not born in that county. He married Susannah Franklin on 28 July 1810 at Hilgay in Norfolk. I believe his parents are John Harply and Frances Crane who married in Hockwold cum Wilton in Norfolk on 17 October 1774.

I have found the following baptisms for children of John and Frances: John, 1776, Sarah 1777, Joseph 1780 and then James (who I believe is my 3x great grandfather) in 1788.

I have met a Peter Harpley who is descended from their first son John. If Peter and I have a DNA test would it tell me if I am also descended from John and Frances Crane? Chris Harpley, via email

AYou could both take a Y-chromosome DNA test and if you have a match this would confirm that you share a common Harpley ancestor. However, the test would not be able to confirm that you are descended from the John Harpley who married Frances Crane, as the same Y-DNA signature is likely to be shared by multiple men with this surname and they could be sharing by virtue of a more distant male-line relationship.

You could both take an autosomal DNA test such as the AncestryDNA test or the Family Tree DNA Family Finder test. Because of the random way in which autosomal DNA is inherited, we are only guaranteed to share enough DNA to show up as a match with cousins up to the second cousin level. If the hypothesis is correct, you and Peter will be fifth cousins and you could potentially share DNA through descent from John Harply and Frances Crane. However, only 32 per cent of fifth cousins will share enough autosomal DNA to show up as a match – see the ISOGG Wiki page on cousin statistics ( isogg.org/wiki/Cousin_statistics). A negative result would, therefore, not rule out a relationship. Other male or female descendants could be tested to see if they match or a fortuitous match may be found in the current databases. Debbie Kennett