Fluorescence micrograph of human chromosomes showing the mapping of cloned fragments of DNA (DNA probes) to the long arms of chromosome 11. In this image, the chromosomes are stained to give red fluorescence, with the probes appearing as areas of green/yellow fluorescence on the ends of the chromosomes. Mapping chromosomes may be regarded as a physical survey of each chromosome to find the location of genes or other markers. Mapping & sequencing (decoding the base-pair sequence of all the DNA in each chromosome) are the two main phases of the human genome project, an ambitious plan to reveal all of the genetic information encoded by every human chromosome.