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Publisher Summary The purpose of mutagenicity is to determine whether a chemical substance has the capacity to cause alteration of genetic information with the potential to produce heritable genetic changes in man. Mutagenicity testing relates not to germ cells but to the somatic cells, where the concern is of cancer. The genetic material of all living organisms, with the exception of certain viruses, is composed of deoxyribonucleic acid (DNA). DNA is a long polymer containing as many as 10 8 nucleotides linked by phosphodiester bonds. There are four main nitrogenous bases that appear in DNA. Two of them are purines, such as adenine and guanine, and the other two are pyrimidines, such as thymine and cytosine. A single chromosome contains as many as 10,000 genes. The core of a chromosome consists of DNA and, therefore, its backbone is the phosphodiester. Chromosomal mutations include either chromosome breaks that would necessarily involve cleavage of the phosphodiester arrangements of the chromosomal segments that are predicated on a combination of phosphodiester breaks and rejoinings of the phosphodiester bonds. The Ames test utilizes several different histidine auxotrophic mutants of Salmonella typhimurium . These bacteria are unable to carry out histidine biosynthesis, and thus are dependent upon an external source of this amino acid for growth. |
