Crowe Genealogy Ireland and the World Pic 1

Specialist y-DNA and mt-DNA testing

What does this special testing tell us?

y-DNA is exclusively male orientated, women do not have a Y chromosome, it is only passed from father to son. It changes very slowly with time over many many generations. it should follow a family surname but we know that it does not always follow, hence y-DNA can be used for paternity testing.

(It is very rare for X and Y chromosomes to swap DNA but it does happen)

Interesting fact: Have you noticed how small the y-chromosome is, especially compared with the x-chromosome? Most of the DNA appears to be redundant too, with very few active genes, the important one determines sex.

mt-DNA is exclusively female and comes from a small organ inside every cell of your body called the mitochondria (mt). One feature of this organ is that it is responsible for making energetic chemicals in your body used by the enzymes in the cell. The sperm does not carry a mitochondria but the egg from the mother does, hence mt-DNA is only passed down to the next generation by the mother's egg. This mitochondria carries a tiny piece of DNA but it can be analysed in the same way as chromosomes. It is much harder to trace it back because women have traditionally changed their names. It is also used for maternity testing.

A quick note on X-DNA

• Both men and women carry an x-chromosome.

• Women always pass one of their x-chromosomes to a son or a daughter.

• The man passes an X to a daughter but not to a son.

• However, the two x-chromosomes in a woman can swap their DNA from her mother’s and father’s Xs and so it is not exclusively 'female' DNA.

What is really useful though is that x-chromosomes DNA changes at a much slower rate than the other 22 chromosomes - at least half as slow? So you may get a distant match here and not on the other chromosomes. Look for intermediates matching you and the other X chromosome match – see Joint matches and Triangulation.

Personal note:

I had intended to get my y-DNA tested. However my personal experience of the groups related to my y-DNA haplogroup and family name had blogs which I can only describe as overtly macho. It is my personal description and knowledge of the dialogues involved but it is my view that this is not a constructive area for my research but more of a tribal position. Hopefully other people will find different in their name groups and if you are adopted or have a real interest it might be something you just have to avoid or counter?

Seamus Crowe     Website2021