The two principal gonadotropins in vertebrates are luteinizing hormone (LH) and follicle-stimulating hormone (FSH), although primates produce a third gonadotropin called chorionic gonadotropin (CG). LH and FSH are heterodimers consisting of two peptide chains, an alpha chain and a beta chain.H and FSH are secreted by the anterior pituitary gland, while hCG and eCG are secreted by the placenta in pregnant humans and mares, respectively. The gonadotropins act on the gonads, controlling gamete and sex hormone production.
Anything that can bring about a mutation in DNA is called a mutagen. Most mutagens fall into one of two categories: They are either a form of energy or a chemical. In addition to X rays, other forms of radiation that can cause mutagens include ultraviolet radiation, gamma rays, and ionizing radiation.
Genetic mutations. Genetic mutations occur when DNA changes, altering the genetic instructions. This may result in a genetic disorder or a change in characteristics. Mutations can be caused by exposure to specific chemicals or radiation. For example, cigarette smoke is full of chemicals that attack and damage DNA. This causes mutations in lung cell genes, including the ones that control growth.