Mapping and sequencing complex genomes: Let's get physical!

Physical maps provide an essential framework for ordering and joining sequence data, genetically mapped markers and large-insert clones in eukaryotic genome projects. A good physical map is also an important resource for cloning specific genes of interest, comparing genomes, and understanding the size and complexity of a genome. Although physical maps are usually taken at face value, a good deal of technology, molecular biology and statistics goes into their making. Understanding the science behind map building is important if users are to critically assess, use and build physical maps.