: a greatly enlarged diplotene chromosome that has apparently filamentous granular loops extending from the chromomeres and is characteristic of some animal oocytes.
What are Polytene and lampbrush chromosomes?
The main difference between polytene and lampbrush chromosome is that polytene chromosomes occur in the salivary glands and other tissues of insects whereas lampbrush chromosomes occur in the oocytes of vertebrates except for mammals and some invertebrates.
What is the function of lampbrush chromosome?
Lampbrush chromosomes are also involved in the production of “masked” mRNAs for early development. The giant granular loops could either be the sites where such mRNAs are packaged or they could be sites where specific alterations of the deoxyribonucleoprotein fiber take place.
What do you mean by lampbrush chromosome?
Lampbrush chromosomes (LBCs) are transcriptionally active chromosomes found in the germinal vesicle (GV) of large oocytes of many vertebrate and invertebrate animals and also in the giant single-celled alga Acetabularia. These cells are all in prophase of the first meiotic division.
Do humans have lampbrush chromosome?
Human and other mammalian chromosomes do not form recognizable lampbrush chromosomes in their own oocytes or in any somatic cells.
How are Lampbrush chromosomes formed?
Chromosomes transform into the lampbrush form during the diplotene stage of meiotic prophase I due to an active transcription of many genes. They are highly extended meiotic half-bivalents, each consisting of 2 sister chromatids.
Which is larger Polytene or Lampbrush chromosome?
There are some probabilities that lampbrush chromosomes help in the formation of certain amount of yolk material for the egg. [II] Polytene chromosomes: These are also giant chromosomes but relatively smaller than lampbrush chromosomes, found in the larvae of certain dipterans.
What is the structure of Lampbrush chromosome?
The lampbrush chromosomes have the lateral loops that extrude from the chromomeres at certain positions. Chromomeres are the beads that appear at the meiosis stage in which the chromosomes resemble a series of beads on a string. The loop is an extruded segment of DNA that is being actively transcribed.
Who observed Lampbrush chromosome?
Lampbrush chromosomes were discovered in sala- mander egg cells (Ambystoma mexicanum) by Flemming in 1882. Ten years later, LBCs were identified in shark egg cells and described by Rückert in 1982. It was Rück- ert who introduced the term “lampbrush chromosome” into biological nomenclature.
What is Lampbrush chromosome Byjus?
Lampbrush chromosomes appear during the diplotene stage of meiosis in a developing oocyte, measuring about 700 m – 5900 m in length. … Hence, chromosomes appear like a lamp cleaning brush. Hence, the name lampbrush chromosomes. The lateral loops are active sites of transcription.
Why lampbrush chromosomes are absent in mammals?
Answer :- Human and other mammalian chromosomes do not form recognizable lampbrush chromosomes in their own oocytes or in any somatic cells.
In which stage of cell cycle lampbrush chromosomes can be seen?
The lampbrush chromosomes occurring in prophase of meiosis I are highly elongated special kind of synapsed mid-prophase or diplotene chromosome bivalents which have already undergone crossing over.
In which of the stage of the growth phase is the Lampbrush chromosome visible?
Note: By the electron microscopy studies in the xenopus laevis oocyte the extension of chromosome axis is seen during the Lampbrush stage of meiotic prophase stage which is linked to the production of high molecular weight non- ribosomal RNA.