The Hunt for a Diagnosis: The Science Bit.

The UK’s first Undiagnosed Children’s Awareness Day is on Saturday 13^th 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 ...

Here's the science bit ... Now pay attention!

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 13^th April.  Please read and share this and the post below to help spread the word.