Trinucleotide repeats are a recent discovery which have provided a molecular explanation for the causes of a number of genetic neurological diseases. The repeats themselves consist of three nucleotides: CAG, CTG, CGG, and have been found in the coding and noncoding sequences of a number of genes. The polymerase chain reaction is a technique that enables DNA amplification for the detection of specific gene sequences or markers. Interferons are glycoprotein cytokines which help cells resist viral replication and regulate the immune response. Oncogenes are genes either viral or mammalian in origin that cause transformation of cells in culture. In the muscle, insulin increases amino acid uptake with increased protein and glycogen synthesis. The actions of insulin are antagonized by oestrogens, growth hormone, thyroxine, glucagon, and cortisol.