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.

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?

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 uses mitochondria to provide energy for motility but it is located in the wall of the sperm and is destroyed once it enters the egg, having delivered the DNA. The only mitochondria left are in the egg. 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

  • Men carry one and women carry two, x-chromosomes.
  • 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 (recombination) from her mother’s and father’s Xs and so it is not exclusively 'female' DNA.  (for the possible routes of inheritance see chart below)

  • What is really useful, x-chromosomes DNA (x-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. However, the amount transferred by a parent may be all or some - it is very erratic and therefore can not be used to guess a generational difference between you and a match.This erratic behaviour can cause some unexpected results too, like the rare case of brothers with the same mother not matching.


    Different for females


    So, females can inherit X-DNA from the father's side of the family as well as the woman's.

    What about Half-siblings?


    More of what is possible and not possible with X-matches and why it is complicated and sometimes seems upsetting.

    x-dna match no match


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