The contraction produced can be described as a twitch, summation, or tetanus, depending on the frequency of action potentials. In skeletal muscles, muscle tension is at its greatest when the muscle is stretched to an intermediate length as described by the length-tension relationship. Smooth and cardiac muscle contractions are myogenic and can be modulated by the autonomic nervous system.
Citation: Pray, L. (2008) Sex-linked diseases: the case of Duchenne muscular dystrophy (DMD). Nature Education 1(1):132. Prenatal diagnostic testing can now determine whether a fetus carries a debilitating or fatal sex-linked mutation.
Sex-linked Traits. If a gene is found only on the X chromosome and not the Y chromosome, it is said to be a sex-linked trait. Because the gene controlling the trait is located on the sex chromosome, sex linkage is linked to the gender of the individual. Usually such genes are found on the X chromosome. The Y chromosome is thus missing such genes (See Diagram above.).