All our genes are inherited in our chromosomes and they contain the biological instructions about how to make our bodies. We get one set of chromosomes from our Mom, another from our Dad. That means we have two copies of most genes in each cell of our bodies.
In a person affected by WS, somewhere along the line, possibly in the formation of the egg or the sperm cell or very early after conception, a random event deletes a small piece from one copy of chromosome 7. The size of the missing piece is slightly different in different people but it often contains 20 to 30 genes and the affected person then has only one copy of these genes rather than the normal two copies.
The absence of these genes on chromosome 7 causes the many different effects we see in a WS person. One gene that is central to this deletion and is absent in a majority of people affected by WS is the gene for a protein called elastin. If you thought that sounds a bit like “elastic” you’d be right.
This protein elastin occurs in the types of muscle that line our blood vessels and the fact people have only one copy not two, may contribute to the fact that many people with WS have conditions which involve narrowing of the blood vessels such as aortic stenosis or renal artery stenosis.
Other genes that are deleted in Williams Syndrome seem to be involved with speech and language, motor co-ordination, and other learning functions. Although the details are not fully understood, the genetic deletion affects many different physical and cognitive or emotional systems leading to the learning disabilities, poor visuo-spatial skills, poor co-ordination and amazingly, their fascination with music in various forms.
I can begin to explain more about what this means, how it happens and how a “simple deletion” can have such a wide range of profound effects but that will come later. Look out for my special science report on the website (http://WilliamsSyndromeAdult.com).