Recombinant DNA technology, in which artificially "cut and pasted" DNA is introduced into living cells, contributed extensively to the rapid development of molecular biology over the past 5 decades since the latter half of the 20 century. Although the original technology required special experiences and skills, the development of polymerase chain reaction (PCR) has greatly eased genetic manipulation for various experimental methods. The current development of a simple genome-editing technique using CRISPR-Cas9 gave great impetus to molecular biology. Genome editing is a major technique for elucidating the functions of many unknown genes. Genetic manipulation technologies rely on enzymes that act on DNA. It involves artificially synthesizing, cleaving, and ligating DNA strands by making good use of DNA-related enzymes present in organisms to maintain their life activities. In this review, I focus on key enzymes involved in the development of genetic manipulation technologies.