Isolation of Genes Coding for Unknown Products - In some cases, we are interested in isolation of a gene whose phenotypic effect is known, but the gene product has not been identified or can not be isolated.

Such genes include those for morphological traits like dormancy, photoperiodicity, disease resistance, etc. This area of research, in which genetics is studied by isolating the gene first without knowing the gene product is often described as reverse genetics.

The methods used for the isolation of these genes are different from those used for genes coding for known proteins. Some of these methods are described in this section.