Final answer:
Reverse genetics starts with the gene to determine its function through mutations or deletions, while forward genetics starts with a phenotype to identify the genes responsible for it.
Step-by-step explanation:
Reverse genetics is a method used to determine the function of a gene by starting with the gene itself. It involves mutating or deleting the gene to observe the resulting phenotypic effects. This approach provides researchers with clues about gene function.
On the other hand, a forward genetics approach starts with a given phenotype and determines the genetic basis of that phenotype. It compares organisms with different phenotypes and identifies the genes responsible for the observed differences.
Contrastingly, forward genetics begins with an unknown gene and involves looking at a phenotype to determine which genes influence it. A classic example of reverse genetics is using reporter genes like GFP to track gene expression.