Reverse genetics defines methods which are used to study the function of a gene and its products from a gene or fragment of DNA. In contrast, classical genetics aim to locate the gene responsible for deterioration of a function or a known characteristic.
When used in inherited diseases it directly identifies the genes involved in inherited diseases for which the defective protein is unknown. It involves a strategy of isolating cloned sequences of genomic DNA involved in an inherited disease.
The information in the nucleotide coding sequences in these is then studied and the protein sequence determined from this.
In molecular virology, reverse genetics defines the generation of the virus whose genome is produced from cDNA (complementary DNA).