DNA topoisomerases play important roles in DNA replication and in supercoiling . These enzymes are also the targets for certain anticancer drugs (see the introduction to this chapter). Eric Nelson and his colleagues studied m-AMSA, one of the anticancer compounds that acts on topoisomerase (E. M. Nelson, K. M. Tewey, and L. F. Liu. 1984. Proceedings of the National Academy of Sciences of the United States of America 81:1361–1365). They found that m-AMSA stabilizes an intermediate produced in the course of topoisomerase action. The intermediate consists of topoisomerase bound to the broken ends of the DNA. Breaks in DNA that are produced by anticancer compounds such as m-AMSA inhibit the replication of the cellular DNA and thus stop cancer cells from proliferating. Explain how m-AMSA and other anticancer agents that target topoisomerase enzymes taking part in replication might lead to DNA breaks and chromosome rearrangements.
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
DNA topoisomerases play important roles in
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