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GLOSSARY
Phage and DNA (Deoxyribonucleic acid)
Phage (or bacteriophage) is a general term for viruses destructive to bacteria. Their existence was first established in 1915 and since that time phages have been studied intensively. In laboratory conditions, their addition to a culture of bacteria in solutioh results in bacteriolysis: the bacteria swell and then suddenly disappear. During this process, the phage enters the bacterial cell and multiplies. Phagcs are angular or spherical in shape, some have a tail. Their size ranges between 8 and 70 millimicron Among the bacteria found to be infested with phage are bacterium, bacillus, micrococcus, corynebacterium,vibrio and actinomyces. Colon bacteriophage is found in human faeces and sewage, dysentery bacteriophage in horse and pig manure, and staphylococcus and streptococcus phage in infected human tissue. Other types of phage are found in soil and decomposed plants. Cultivation and examination of phages,using an electron microscope, is relatively simple and their study has become an important field of bacteriology. In order to unify research, the most widely-used phage for research purposes is the T system which infests strain B of E coli.DNA, or deoxyribonucleic acid, is a polymer of nucleotides made up of one part of phosphoric acid, one part of D-deoxyribose sugar and one part of purine or pyrimidine base. It has been established that DNA is a carrier of genetic information within the nucleus of all living cells and much complex rcsearch has been done into the structure of DNA and the so-called "genetic code": Phages, which contain DNA, have played an important part in these genetic studies.