The metabolic stability and the reactivity of a library of candidate drug compounds have to be assessed for drug metabolism and toxicological studies. Many methods have been proposed for quantitative predictions in drug metabolism; one example of a recent computational method is SPORCalc .  If the chemical structure of a medicinal compound is altered slightly, this could slightly or dramatically alter the medicinal properties of the compound depending on the level of alteration as it relates to the structural composition of the substrate or receptor site on which it exerts its medicinal effect, a concept referred to as the structural activity relationship (SAR). This means that when a useful activity has been identified, chemists will make many similar compounds called analogues, in an attempt to maximize the desired medicinal effect(s) of the compound. This development phase can take anywhere from a few years to a decade or more and is very expensive. 
This module introduces the processes involved in maintaining genome stability, causing genome variability and controlling the coding potential of the genome. Mutation, recombination and transposition, and the interplay between them, are examined as causes of genome instability. The two main themes of the module are the impact of genome instability/change upon gene expression, and its control. An introduction to bioinformatics and sequence analysis with the use of sequence databases and analysis tools permits the analysis of gene/genome variability with an introduction to the importance of bioscience research, including molecular diagnostics and drug development.