Basic Molecular Biology & Techniques - Recent Advances

Genetics focuses on the nature of genes, and a major goal is to characterize their structure and function. Recombinant DNA technology has allowed individual genes to be isolated in a test tube and then characterized at the molecular level. The technology is based on restriction enzymes, which cut DNA into defined fragments. Restriction target sites can be mapped and act as DNA landmarks. Restriction fragments often have sticky ends, enabling them to be inserted into a vector capable of replicating in a bacterial cell. Such molecular hybrids are known as recombinant DNA. Bacteria amplify a single recombinant DNA molecule to form a DNA clone. Common vectors are plasmids, phages, and cosmids. An entire genome can be cloned in a set of clones known as a library. A specific clone can be found in a library by using a probe that specifically binds to the DNA or to the protein of the desired clone. Specific clones can also be isolated by their ability to transform null mutants. Tagging also is useful for cloning a gene: transforming DNA or a transposon is used to cause a mutation by insertion.