D. Stussy wrote:
> "Steve Hayes" <hayesmstw@[EMAIL PROTECTED]
> wrote in message
> news:u83iq3d8vfgnddl8566tsd9hug2ihju95m@[EMAIL PROTECTED]
>> If this goes any further, we may need genealogy software that allows
one
> to
>> enter three or more parents - and what would a pedigree chart look like
> then?
>> http://news.yahoo.com/s/ap/20080205/ap_on_sc/embryo_research
>>
>> LONDON - British scientists say they have created human embryos
containing
> DNA
>> from two women and a man in a procedure that researchers hope might be
> used
>> one day to produce embryos free of inherited diseases.
>> ...
>
> Very good question. However, this can also be called genetic
engineering
> and thus there may be NO parents!
>
> I think you're getting ahead of us. How much of a DNA contribution is
> worthy of note?
The three people involved contributed DNA as follows:
Mother: 23 chromosomes, around 3 billion DNA "letters"
Father: 23 chromosomes, around 3 billion DNA "letters"
Egg donor woman: mitochondrial DNA, about 16,000 DNA "letters"
The mitochondria are sometimes called the "power plants" of the cell
because they produce ATP, a molecule that is an essential source of
energy for all of the other chemical processes going on within a cell.
The fact that they have their own DNA, independent of the nucleus of the
cell, is intriguing, and has led biologists to hypothesise that the
mitochondria are actually descendants of ancient bacteria which formed a
symbiotic relation****p with other organisms early in the history of
multi-cellular life on Earth.
However, the mitochondrial DNA is tiny in comparison with the 46
chromosomes that we inherit from our parents: 16,000 DNA "letters"
compared to six billion. It is also tiny in terms of the number of
genes it contains: a mere 37, compared to the estimated 20,000 to 25,000
genes that are contained in the chromosomes.
The mitochondrial DNA does not carry any of the genes for
characteristics that we normally regard as inherited, such as hair
colour, height, and so forth. In that sense, it doesn't make much of a
contribution from a genealogical standpoint.
However, it can, unfortunately, contain errors, and these can give rise
to genetic defects in the same way as defective genes on the
chromosomes. A mother with a genetic defect in her mitochondrial DNA
would pass that on to all of her children, since we inherit our
mitochondrial DNA solely from our mothers.
The purpose of the research that was re****ted this week is to help such
women to have healthy children. The donor woman would be someone
without a defect in the mitochondrial DNA.
I hope this helps to clarify things.
David Harper
Cambridge, England
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