Forward Genetics
This starts with a phenotype and uses this to try and identify and establish the function of the gene that causes it. Instead of knocking the known gene out and looking at the consequences, random mutations are introduced into the genome and the consequences of these on the phenotype produced are examined.
To begin this process a screen needs to be set up in which the expression of a marker gene is induced. Then random mutations are introduced into the genome and interesting phenotypes are selected for analysis.
To identify a gene’s function the techniques used include linkage analysis, expression vectors, epitope tags, and GFP transgenic lines.
Linkage Analysis
The aim in this approach is to find the approximate location of a gene relative to gene marker whose position is already known. A genetic marker is a piece of DNA whose physical location on a chromosome is known. It can be a gene or a piece of DNA with unknown function. The process of linkage analysis is based on the recombination of homologous chromosomes, and it is often used to search for the position of human disease genes. To investigate this in more detail visit the Human Genome site.