Radiation hybrid mapping (also known as RH mapping) is a technique for mapping mammalian

chromosomes A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

. Radiation hybrid mapping consists of several steps. First of all, desired chromosomes are broken into several segments with

X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency, ...

, after which they are implanted in rodent cells, which clone the chromosomes. Then these clones are analyzed for the presence of certain

DNA marker A genetic marker is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can be ...

s. If two given DNA markers are far apart on the initial chromosome, then it is likely that they will appear in distinct fragments. The frequency of the separation of the markers into different fragments is used to estimate the chromosomal distance between them. The RH procedure was used to map 14 DNA probes from a region of human chromosome 21 spanning 20 megabase pairs.

References

Chromosomes {{genetics-stub