Virus and spyware definitions are files that act like an encyclopedia of known malicious software, including viruses, spyware, and other potentially unwanted software.
Highly accurate DNA parental testing became available in the 1980s with the development of RFLP. In the 1990s, PCR, developed in 1983, became the standard method for DNA parental testing. A simpler, faster, and more accurate method of testing than RFLP, it has an exclusion rate of 99.99% or higher.
DNA was then found in the nucleus of all eukaryotic cells. During the 1920s, biochemist P.A. Levene analyzed the components of the DNA molecule. He found it contained four nitrogenous bases: cytosine, thymine, adenine, and guanine; deoxyribose sugar; and a phosphate group.