lampbrush chromosome One of the large chromosomes found in the eggs (primary oocytes) of amphibians, with paired loops which extend from most of their chromomeres giving a furry, brush-like appearance under the microscope. They are particularly obvious at the diplotene stage of meiosis.

lampbrush chromosome A type of chromosome found in the oocytes of animals, notably newts and other amphibians, that is characterized by having numerous loops arising from the long axis of the chromosomal arms. Under the microscope this gives an appearance reminiscent of a cylindrical brush of the type formerly used for cleaning oil lamps. The loops are regions where the chromosome is uncoiled and the DNA exposed for active transcription by an associated matrix of RNA and proteins.