Molecular model of the extended messenger RNA (ribonucleic acid) molecule produced in type 2 myotonic dystrophy (DM2). DM2 is a genetic disease that causes muscle loss and weakness that gets worse over time. The muscles are also often unable to relax after use. It is caused by a segment of DNA being repeated an abnormal number of times. When the DNA is transcribed to mRNA it produces an unusually long mRNA molecule that forms clumps in the cell. The clumps interfere with the production of proteins and prevent the normal functioning of the cell, leading to the symptoms of DM2.