With termination, a stop codon is reached and the polypeptide chain is released into the cytoplasm or enters the cytomembrane system for further processing. In cells that are rapidly making proteins, polysomes consisting of many ribosomes are translating the same mRNA transcript to make polypeptides in a hurry. Newly synthesized polypeptides either join the cytoplasm's pool of proteins or enter the cytomembrane system in preparation for export. B. Common Gene Mutations and Their Sources 1. C. Causes of Gene Mutations 1.
Many gene mutations are spontaneous.
Others are caused by mutagens such as UV light, ionizing radiation, and alkylating agents. The Proof Is in the Protein 1. Spontaneous mutations are rare and will not endure unless they occur in gametes. A protein that is specified by a heritable mutation may have harmful, neutral, or beneficial effects on an individual's ability to function in the prevailing environment.