Mosomes in the larval salivary glands so that clones can be assigned positions in the genome by means of in situ hybridization. Drosophila is unique among model organisms in presenting giant polytene chro. In most organisms, sets of overlapping clones covering an uninterrupted stretch of the genome (contigs) are assembled by detecting overlaps by means of shared restriction fragments in fingerprints or shared sequence-tagged sites (STS). There is also a first-generation physical map of the human genome (Cohen et al., 1993). These include Escherichia coli (Kohara et al., 1987), Saccharomyces cerevisiae (Olson et al., 1986), Caenorhabditis elegans (Coulson et al., 1986), and Drosophila melanogaster (Hartl, 1992). A clone-based physical map also opens up new opportunities for studies of genome evolution.Ĭlone-based physical maps have been assembled for several species chosen as model organisms in the Human Genome Project (Collins and Galas, 1993).

The map facilitates the molecular identification of mutant genes, and the clones in the map provide ready access to substrates for genomic sequencing. Such a map affords a unique resource for studying the structure and function of the genome. LozovskayaĪ clone-based physical map consists of a set of ordered, overlapping inserts of cloned genomic DNA. Comparison of the two molecular maps indicates a one-to-one topographical correlation between the genetic and chromomeric units.Genome Structure and Evolution in Drosophila: Applications of the Framework P1 Mapĭaniel L. By mapping the breakpoints of deletions within the 315 kb region, we have located its 12 lethal complementation groups, which include the genes coding for acetylcholinesterase (Ace) and xanthine dehydrogenase (rosy). The length of the largest chromomeric unit within the 315 kb region is approximately 160 kb, while that for the smallest is less than 7 kb and may be as short as 3 kb. The molecular map positions of the 13 +/- 1 chromomeric units from the 87D5-6 to 87E5, 6 region of the third chromosome were determined by in situ hybridization of selected segments to the polytene chromosomes. We have used a set of overlapping cloned segments defining a 315 kb (X 10(3) base-pairs) region of Drosophila melanogaster chromosomal DNA to map the sequences associated with the polytene band-interbands (chromomeric units) and with the lethal complementation groups contained within this region.

Drosophila chromosome map