Facio Scapulo Humeral MD Explained
How is it inherited?
A separate gene determines each hereditary characteristic or function. These genes are packed together into chromosomes like beads on a string. There are two copies of each chromosome (excepting the X and Y chromosomes in males), and hence two copies of each gene (a pair), coming one from each parent. The ‘gene' for FSHD is at one end of each copy of chromosome 4. In FSHD, one copy of this particular pair is faulty (part of it is missing, which is referred to as a ‘deletion'). Hence there is a 50:50 (1 in 2) chance for each of the offspring of an affected parent to inherit the faulty copy, resulting in FSHD. They also have an equal chance of inheriting the good copy (resulting in no risk for these individuals or their descendants of being affected by FSHD). This pattern of inheritance is called ‘autosomal dominant'.
With completion of the ‘human genome project' has the gene causing FSHD been identified?
Unfortunately the situation is a little more complex than as discussed (in answer 12.) above. Amongst genetic conditions, FSHD seems so far to be unique in that the genetic fault (‘mutation') is the reduction (‘deletion' at one end of chromosome 4) of multiple copies of a repeated sequence of DNA (likened to reducing the number of carriages in a train). This DNA change, which is the dominantly inherited factor, is probably exerting an effect on the way that the function of many genes is regulated in muscle, and particularly in the muscles of the face and shoulder girdle. Hence, there may be many ‘genes' which are involved in causing FSHD, but for which the controlling dominantly inherited mutation always occurs at the same place on chromosome 4. Much current research in FSHD is aimed at trying to define this link.
|
paypal