Scientists expect that having a detailed map of the entire set of human genes will revolutionize medical practice and biomedical research. The Human Genome Project is focusing on the creation of genome maps , both genetic linkage maps and physical maps . Genome maps depict the order in which genes, genetic markers , and other landmarks are found along the chromosomes.
Linkage maps exploit a phenomenon called recombination or crossing over .
As developing sperm and egg cells divide, pairs of maternal and paternal chromosomes sometimes break and exchange pieces with one another. In 1994, international collaborators published a comprehensive linkage map charting more than 5,000 markers and more than 400 genes. After scientists use genetic linkage maps to assign a gene to a relatively small area on a chromosome, they next examine the region up close to learn the gene's precise location. To do this, scientists turn to physical maps. Scientists then copy or clone the pieces in the laboratory, obtaining millions of identical copies of specific DNA segments.