Scientists at a Scottish university have made a discovery that could help explain the most common genetic cause of death in children.

Spinal muscular atrophy (SMA), also known as floppy baby syndrome, targets the body's nerve cells (motor neurones), causing babies to have little or no control over their movements.

SMA, which is currently incurable, is the leading genetic cause of death in children and affects one in 6000 births.

The disease causes the loss of motor neurons in the spinal cord, leading to muscle wasting, paralysis and respiratory failure.

Cell biology experts at the University of St Andrews have now found differences in the movement of key parts of a molecular "machine" called the spliceosome which is vital to the way genes work. It helps to decode the DNA molecules that carry genetic instructions and removes sections which are not needed.

This decoding process goes wrong in conditions such as SMA.

Now the researchers hope the discovery of these differences in molecular movements may help explain what goes wrong in cells to cause the condition.

The gene responsible is known but it is still not clear how problems with this gene damage the cells of the body and why motor neurons, responsible for sending messages to the muscles, are particularly sensitive.

The more researchers can find out about how cells are damaged in SMA, the better the chance of finding treatments, the scientists said.

Dr Judith Sleeman, who led the research being published in the Journal of Cell Science, said: "The genetic defect that causes SMA has been known for nearly 20 years, but how this defect leads to the symptoms is still not understood.

"Problems with the splicing of messenger RNA, an essential step in decoding genes, have been seen in SMA. Our work explains how these problems might be caused.

"We hope that this will provide an important clue to help unravel how cells are damaged in SMA and, in time, contribute to the development of treatments for this devastating condition."