An Introduction to Genetic Engineering

In Chapter 10, the methods used to identify and select specific clones from clone banks (libraries) are described. The terms selection and screening are defined, and selection using selectable markers for antibiotic resistance is outlined as an example. Other genetic selection methods such as use of chromogenic substrates, insertional inactivation and complementation of defined mutations are described. Screening clone banks with nucleic acid probes and hybridisation methods is outlined to illustrate the powerful and specific nature of this approach. Radioactive and non-radioactive labelling techniques are compared, with the advantages and disadvantages of each outlined. The use of the polymerase chain reaction in screening, and immunological screening for expressed genes are described. Automation of screening is discussed to illustrate how high-throughput screening protocols enable very large numbers of clones to be screened efficiently. Analysis of cloned genes is described, covering techniques such as restriction mapping, Southern blotting and its derivative methods, sub-cloning and DNA sequencing.