Sunday, March 18, 2007

Happy Medical Mothers Day

Today is the wonderful celebration of 'Mothering Sunday'. There are so many things to thank my own mother for that I couldn't possibly write them all here. However, the one thing we can collectively thank our mother's for, is mtDNA (mitochondrial DNA).

Whenever an egg cell is fertilized, nuclear chromosomes from a sperm cell combine with the egg's nuclear DNA, producing a mixture of both parents' genetic code. However, the mtDNA from the sperm cell is left behind outside of the egg cell. Hence, the fertilized egg contains a mixture of the father and mother's nuclear DNA and an exact copy of the mother's mtDNA, but none of the father's mtDNA.

The result is that mtDNA is only passed on along the maternal line. This means that all of the mtDNA in the cells of a person's body are copies of his or her mother's mtDNA, and all of the mother's mtDNA is a copy of her mother's, and so on. No matter how far back you go, mtDNA is always inherited only from the mother.

May I wish you all a Happy Mother's Day.


simon said...

what does it mean? In terms of the person.. you inherit certain aspects that are only passed through the mother?

Dr Michelle Tempest said...

Hi Simon, It is thought that it's only mtDNA which is exclusive to the mother's genetic line.... everything else is 50:50. Thanks for the comment. Michelle

Anonymous said...

How interesting I did not know that. Thanks Michelle.

Peter Smallbone said...

As a Biology graduate, I recall this mtDNA stuff with fondness.

mtDNA is particularly useful in population genetics and evolutionary biology, because unlike chromosomal DNA, you don't get bits from both parents recombining. Therefore, differences between individuals are only down to mutations and inheritance from single, but different, genetic lines (the maternal).

When I studied this, there was the concept of 'mitochondrial Eve' being banded about, which is the prehistoric female from which all our versions of mtDNA are derived. I don't know whether this concept is still 'en vogue', but it always struck me as a bit arbitrary, and not necessarily that well aligned with the point of origin of Homo sapiens.

mtDNA was used in the study of the genetic composition of African Americans. It was known that a certain proportion (I think up to 25%) of DNA in this population probably originated from Europeans. It had long been postulated that this was caused by white, male slave-owners taking advantage of their female slaves. When mtDNA was investigated, it was shown that as much of this European DNA was of maternal origin, i.e. originating from white women.

David Anthony said...

It slipped my mind to thank my mother for her mtDNA. It could make for an interesting card for next year. Thanks for the tip.

Anonymous said...

"Mum" is my favourite word, I love hearing it said, and also my favourite full time occupation!

Ju's little sister said...

As far as I have been able to understand, mtDNA can be grouped, world-wide into about seven or so main groups. Mitochondrial Eve was simply a description of the source of mtDNA which all others have since mutated away from.

I have heard that it has been discovered mtDNA does in fact share its genes, and does not replicate by exact cloning as it had been supposed.

Can anyone back that up, or destroy it for me?

Liz Hinds said...

If my children get this thing from me and I got it from my mother who got it from her mother, does it mean that somewhere in the long distant past, we all came from the same one? What is her name? The woman in Africa?