The UK’s first Undiagnosed Children’s
Awareness Day is on Saturday 13th April, so in order to do my bit
and raise awareness for such a worthy cause, I’m going to take you right back
to the beginning and explain my Little H’s lack of diagnosis. Today’s the Science Bit – it’s all
about chromosomes and genetics and translocations and things I’d no knowledge of
until Little H came along and wowed us all with his own very unique blend of
chromosomes! (Don’t tell my A’ Level
Biology teacher I’ve just admitted knowing nothing about chromosomes).
So ... How can Little H have a diagnosis of a rare chromosome disorder and still be undiagnosed? Well it’s not
that simple ...
Inside every cell of our
bodies (except the red blood cells) we have a nucleus and inside this are
chromosomes. They're long and thread-like in structure and are made up of
DNA and proteins. Special stretches of DNA are genes and it is these genes
that tell our bodies how to develop and how to function properly.
Apart from the egg cell in the female and the
sperm in the male, each cell normally contains 23 pairs of chromosomes, that's
46 altogether. They are named as numbered pairs from 1-22 and the 23rd
pair are called the sex chromosomes, labelled X or Y. Males usually have
an X and a Y, whereas females usually have two X's.
Chromosomal abnormalities can occur when there
are extra chromosomes (for example Down Syndrome) or missing chromosomes.
They can also occur when the chromosomes are rearranged and small parts
of the chromosome are added or deleted - this is known as micro-duplications or
micro-deletions.
Sometimes the chromosomes just get a bit mixed
up - this is called a translocation and as long as there is no material missing
or added (a micro-deletion or micro-duplication) then this shouldn't cause any
problems at all. Many normally functioning members of the public may
unwittingly have these 'balanced translocations' with little or no effect.
H appears to have a balanced translocation.
In six different places, his chromosomes have broken and reattached
somewhere else, though there is no evidence of any material missing. On
the face of it he shouldn't have any problems at all. But clearly he
does. And since with every break point, the chance of losing a small
amount of genetic information increases (even if we can't see it yet) the fact
Little H has six mean that it is highly likely that at least one of these
breaks is the cause of H's difficulties.
To have chromosomes as dramatically rearranged
as H's is quite unusual. At present there is no-one else in the world
with his exact rearrangement of chromosomes. He is entirely unique!
In time, with greater chromosomal analysis we may be given a series of
numbers and letters which indicate the specific point on the chromosome that is
responsible for his special needs and then we may find someone else with a
deletion in the same place, but for now, as far as we know, he is entirely one
of a kind.
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This post is part of a blog
hop to raise awareness of undiagnosed genetic conditions for Undiagnosed
Children’s Day on 13th April.
Please read and share this and the post below to help spread the word.
I have extra genetic material on my third choromosome. I found that out through genetic testing regarding my son so it basically means nothing. I call it my floating space debris. I find all of this science stuff quite amazing. Thanks for the lesson.
ReplyDeleteFloating space debris? I like that. I found I've got an inversion through the same tests. I call it 'an upside down bit' which sounds much less exciting than floating space debris. I think I'll have to rename it! :)
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