The Genome

One thing I can definitely say is that my knowledge of biology has improved enormously over the past 9 years and one area which I have found particularly fascinating in the subject of genetics.

Every human body is comprised of about 100 trillion (a hundred million million) cells and inside every one of these cell is a copy of your genome which contains 46 packages of DNA each package being a Chromosome. As I wrote in my Day 5 Blog- Striped Socks, 23 of these packages came from Mum and the other 23 came from Dad.

The DNA molecule is called the building block of life, a giant instruction manual for the body.  The DNA molecule is a double helix structure which looks like a twisting ladder with each rung of the ladder made up of one of four chemicals adenine (A), thymine (T), cytosine (C) and guanine (G).

Double Helix

The22Crew logo inspired by the Double Helix

Each pair of chemicals is referred to as a base pair and the human body is comprised of around 3 billion base pairs. The base pairs are not spread evenly among the chromosomes. Chromosome 1 is the largest with about 250 million base pairs with Chromosomes 21 and 22 being the smallest with around 50mm base pairs each.  Chromosome 22 holds around 1.7% of the body's DNA and the amount of genetic material lost as a result of 22q11.2DS is approximately 3 million base pairs or 0.1% of the total.

Individual segments of the DNA strand contain the genetic code to make proteins and each of these protein making segments is called a gene. A human body has around 20,000 genes and 22q is believed to affect approximately 30-40 genes.

The amount of genetic material missing in a person with the deletion is a tiny amount of the total, 0.1% of DNA and less than 0.2% of genes but it is amazing that such a small amount of missing genetic material is responsible for over 180 anomalies.

In April 2003 the Human Genome Project was completed and this provided for the first time the complete list of the base pairs which make up the human DNA sequence.

Research continues to progress and now scientists are looking into individual genes and the proteins they make to see how they affect the body.

Once such gene being investigate is called TBX1 which is found on the long arm (q) of Chromosome 22 at location 11.21. Experiments with mice who are missing gene TBX1 have shown similar cardiac anomalies to these found in humans. It is therefore believed that absence of TBX1 is a key factor in 22q11.2 DS.

At the VCFSEF conference in Dublin last year there was a presentation on the effect of another gene COMT. The enzyme made by the COMT gene is responsible for breaking down dopamine. Too little of this enzyme may affect the dopamine system and it is suspected that schizophrenia which is significantly higher in people with 22q (See Day 17 post - 1 in 4) may be caused by an overactive dopamine system.

These are just two of the many genes currently being researched and I think the study of individual genes and proteins is very exciting.

Only last week The Economist newspaper (http://www.economist.com/news/science-and-technology/21601809-potent-source-genetic-variation-cognitive-ability-has-just-been) reported about research on a protein klotho made by a gene called KL. The research showed that a version of the gene KL-VS promoted longevity and improved cognitive ability by 6 IQ points.  The article suggested that if a drug can be produced to boost levels of klotho this could be used boosts a person's mental ability.

This may be a long way off but I can see the day when there could be a range new drugs to help people with 22q.