Chromosome Walking

Sometimes a gene product for a gene in question is not known, but the gene still needs to be isolated. A scenario such as this requires an alternate approach technologically.

A chromsome walk is when a DNA fragment form a nearby region is designated as a starting point which begins repeated screenings but in such a way as to produce overlapping fragments of the DNA. With each cloning of the fragment, the overall size of the fragment increases, allowing observers to "walk" down the dNA to the desired location.

In screening large libraries in which rather large introns are involved, several recombinants may be identified. However, the recombinants may contain complementary sequences but not be contiguous. Chromosome walking allows the recombinants to become linked.