Clone Maps: Clone maps are constructed using a clone library consisting of a large number of fragments of the DNA target, possibly existing in multiple quantities. The idea is that a typical target position is covered multiple times by different clones. We saw last time how this library could be constructed via appropriate experiments. The map is constructed by looking at the overlap structure of the clones in the library. The sizes of the clones depend upon the particular vector used. For example, M13-clones are about 3KB long, λ-clones are about 15KB, and YACs (yeast artificial chromosomes) can be more than a megabase in size.