Molecular biology

18.1: Viruses and Bacteria Viruses What is a Virus? Virus: composed of nucleic acids enclosed in a protein coat and are smaller than the smallest bacterium Biologists consider viruses to be nonliving because viruses are not cells. Viruses do not carry out respiration, grow or develop. Viruses can only multiply when they are inside a living cell. Host cell: cell in which a virus replicates Almost all viruses are parasites because they destroy the cells in which they multiply. Viruses can infect the organisms of all six kingdoms. Because viruses are not alive, scientists do not use binomial nomenclature to name them.

DNA and Genes (Extended Notes) DNA: The Molecule of Heredity What is DNA? An organism?s environment influences how an organism develops, but the organism?s DNA holds the genetic information and determines its traits. DNA achieves this by controlling the structure of proteins. Your body is made up of proteins Your body?s functions depend on proteins called enzymes In the 1950s scientists thought protein was the genetic material In 1952 Hershey and Chase infected bacteria with radioactive viruses (one was radioactive protein & the other was radioactive DNA) Only the radioactive DNA entered the bacteria and produced new viruses DNA is a complex organic molecule called a polymer. The monomers, or repeating subunits, that make up DNA are called nucleotides.