Lampbrush chromosome are a special form of chromosome found in the growing

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female g ...

s (immature eggs) of most animals, except mammals. They were first described by

Walther Flemming Walther Flemming (21 April 1843 – 4 August 1905) was a German biologist and a founder of cytogenetics. He was born in Sachsenberg (now part of Schwerin) as the fifth child and only son of the psychiatrist Carl Friedrich Flemming (1799–1880 ...

and Ruckert in 1882. Lampbrush chromosomes of tailed and tailless amphibians, birds and insects are described best of all.

Chromosome 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 ar ...

s transform into the lampbrush form during the diplotene stage of meiotic

prophase I Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r ...

due to an active

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

of many genes. They are highly extended meiotic half-bivalents, each consisting of 2 sister chromatids. Lampbrush chromosomes are clearly visible even in the

light microscope The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microsc ...

, where they are seen to be organized into a series of chromomeres with large chromatin loops extended laterally. Continuous RNA transcription is required to maintain typical chromomere-loop structure of lampbrush chromosomes. Inhibition of transcription leads to retraction of lateral loops into chromomeres and chromosome condensation. Lampbrush chromosomes produce a large number of mRNAs and non-coding RNAs, which are synthesized on the lateral loops. These transcripts are used during oogenesis and at the early stages of embryogenesis. Each lateral loop contains one or several transcription units with polarized RNP-matrix coating the DNA axis of the loop. Amphibian and avian lampbrush chromosomes can be microsurgically isolated from oocyte

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...

(germinal vesicle) with either forceps or needles. Giant chromosomes in the lampbrush form are useful model for studying

chromosome 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 ar ...

organization,

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...

function and

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ...

expression during meiotic prophase, since they allow the individual transcription units to be visualized. Moreover, lampbrush chromosomes are widely used for high-resolution mapping of DNA sequences and construction of detail cytological maps of individual chromosomes.Gaginskaya E, Kulikova T, Krasikova A (2009) Avian Lampbrush Chromosomes: a Powerful Tool for Exploration of Genome Expression. Cytogenet Genome Res. V.124. P.251–267.

References

General * Flemming W (1882) Zellsubstanz, Kern- und Zelltheilung. Vogel, Leipzig. * Rückert J (1892) Zur Entwicklungsgeschichte des Ovarialeies bei Selachiern. Anat Anz 7: 107–158. * Gall JG (1966) Techniques for the study of lampbrush chromosomes. In: Prescott DM (ed) Methods in cell physiology, vol II. Academic Press, London New York, pp 37–60. *Gall J.G., Callan H.G. H3 uridine incorporation in lampbrush chromosomes. Proc. Natl. Acad. Sci. USA. 1962. Vol. 48. P. 562–570. * Callan HG (1986) Lampbrush Chromosomes. Springer-Verlag, Berlin, Heidelberg. 252pp. * Macgregor HC (1984) Lampbrush chromosomes and gene utilisation in meiotic prophase. In: Controlling Events in Meiosis, W. Evans and H.G.Dickinson (Editors). The Company of Biologists. P 333–348. * Macgregor HC, Varley J (1988) Working with Animal Chromosomes. 2nd edition. John Wiley & Sons. * Morgan, G.T. (2002) Lampbrush chromosomes and associated bodies: new insights into principles of nuclear structure and function. Chromosome Research. 10: 177–200. * Alberts, Johnson, Lewis, Raff, Roberts, Walter (2008), "Molecular biology of the cell" 5th edition. (p234–235). * Gaginskaya E, Kulikova T, Krasikova A (2009) Avian Lampbrush Chromosomes: a Powerful Tool for Exploration of Genome Expression. Cytogenet Genome Res. V.124. P.251–267. *Macgregor H.C. Chromomeres revisited. Chromosome Res. 2012. V. 20. P. 911–924. *Chromosome Research
Special Issue (2012) "Lampbrush Chromosomes"
Edited by Herbert Macgregor. Specific

External links

{{commons category, Lampbrush chromosomes
A site introducing a remarkable form of chromosome that exists during the extended diplotene phase of meiosis in the growing ovarian eggs of all animals except mammals. Compiled and edited by Herbert Macgregor, School of Biosciences, University of Exeter.

Methods for making lampbrush chromosome preparations from oocytes
Chromosomes