Muscle cells contract in complex mechanical and chemical processes. If any part of the process or structure is disrupted, dysfunction will likely result, as in the case of those with genetic variations. In those with nemaline myopathy, muscle contraction is adversely affected. At the electron microscopic level, rod-shaped components can often be seen in some of the muscle cells, and when seen, are diagnostic for the condition called nemaline rod myopathy. The presence of these rods is not itself causing muscle weakness; rather they appear as a result of something going wrong within the muscle fiber. There is no connection between the number of rods found in the muscle cells and the amount of weakness a person has. All of the different gene mutations leading to the condition called nemaline myopathy that have been found so far are in genes that encode different components of the sarcomere. In normal muscle cells, the various parts of the muscle fibers that make up the sarcomere are distributed evenly in a pattern for effective muscle contraction. Evidence suggests that some kinds of NM affect the arrangement of these muscle fibers, causing the muscles to be unable to contract as efficiently or effectively.