The lowest resolution physical map is the chromosomal or cytogenetic map, which is based on the banding patterns of stained chromosomes observed through a light microscope. The more detailed cosmid contig map depicts the order of overlapping DNA fragments spanning the genome. A macro restriction map describes the order and distance between enzyme cleavage sites. The highest- resolution physical map is the complete DNA base pair sequence of each chromosome. Another way that scientists are studying the genes is by studying the proteins for which these genes code.
Computers now analyze the structure of proteins, determining how they fold, and their functions.
This data is then used to find the gene in the chromosome. There are about 4,000 hereditary diseases that seem tobe caused by a defect in a single gene somewhere in the genome. For instance, the cystic fibrosis gene is a 250,000 base pair gene and the only thing different from disease-causing and normal genes is that one base pair triplet is missing out of the middle. Although researchers still look for a single gene that could be the cause of a problem, emphasis is now being placed on more complex diseases, like heart disease, cancer, psychiatric disorders, and diabetes, where there are almost surely multiple genes involved. While the initial thrust of the genome project is to sequence and identify genes, researchers are already gearing up to use this information in the study of diseases.