LAMPBRUSH CHROMOSOME PDF

You are on page 1of 13 Search inside document Lampbrush Chromosome Lampbrush Chromosome First seen by Flemming in It is the largest chromosome known and is found in the amphibian oocytes immature eggs. Also seen in diplotene in oocytes of fish, birds, reptiles, and some invertebrates. Lampbrush chromosomes occur during the diplotene stage of meiosis I. They are meiotic bivalents, each consisting of each consisting of two pairs of sister chromatids. Lampbrush chromosomes are so called because the chromosomes seem to have a chromomeric pattern with loops projecting in pair from majority of chromosomes and they appear like the brushes, that were used for cleaning glass chimneys of Kerosene lamps.

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You are on page 1of 13 Search inside document Lampbrush Chromosome Lampbrush Chromosome First seen by Flemming in It is the largest chromosome known and is found in the amphibian oocytes immature eggs.

Also seen in diplotene in oocytes of fish, birds, reptiles, and some invertebrates. Lampbrush chromosomes occur during the diplotene stage of meiosis I. They are meiotic bivalents, each consisting of each consisting of two pairs of sister chromatids.

Lampbrush chromosomes are so called because the chromosomes seem to have a chromomeric pattern with loops projecting in pair from majority of chromosomes and they appear like the brushes, that were used for cleaning glass chimneys of Kerosene lamps. First observed by Flemming in and were decribed in detail in shark oocyte by J. Ruckert in who later coined the name. In vertebrates during the diplotene stage of meiosis, lampbrush chromosomes discovered by Ruckert in are formed in the nuclei of yolk rich oocytes during the active synthesis of mRNA molecules for the future use by the egg during cleavage when no synthesis of mRNA molecules is possible due to active involvement of chromosomes in the mitotic cell division.

It is larger in size. Hence it is called a giant chromosome. Lampbrush chromosomes are clearly visible even in the light microscope, where they are seen to be organized into a series of large chromatin loops emanating from a linear chromosomal axis giving a furry, brush-like appearance.

Each lamp brush chromosome consists of a main axis and many lateral loops. The main axis of each chromosome is formed of 4 chromatids. The main axis contains a series of thickenings called chromomere.

From each chromomere a pair of lateral loops arise one on each side. Each loop has an axial fibre, which is a continuation of the chromonema of the main axis. Loops have transcriptional activity. The axial fibre of the loop is surrounded by a matrix. The matrix is formed gives a fuzzy appearance. The synthesis of proteins and yolk takes in the lateral loops These chromosomes are producing large amounts of RNA for the oocyte, and most of the genes present in the DNA loops are being actively expressed.

The majority of the DNA, however, is not in loops but remains highly condensed in the chromomeres on the axis, where genes are generally not expressed. Giant chromosomes in the lampbrush form are useful model for studying chromosome organization and gene expression during meiotic prophase, since they allow the individual transcription units to be visualized.

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Lampbrush Chromosome

Continue Reading Loading… They are named so because of the structure observed under light microscope resemble to the brush used for cleaning chimneys. These are the largest known chromosomes found in the yolk rich oocytic nuclei of certain vertebrates such as fishes, amphibians, reptiles and birds. They can be seen with naked eye and are characterized by fine lateral loops, arising from the chromomeres, during first prophase diplotene of meiosis. These loops give it a brush-like appearance; that is why these are called lampbrush chromosomes first discovered by Flemming in and were described in shark oocytes.

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Lampbrush chromosome

They can be seen with naked eye and are characterized by fine lateral loops, arising from the chromomeres, during first prophase diplotene of meiosis. Image Courtesy : researcher. It consists of longitudinal axis formed by a single DNA molecule along which several hundred bead-like chromomeres are distributed in a linear fashion. From each chromomere there emerge two symmetrical lateral loops one for each chromatid , which are able to expand or contract in response to various environmental conditions.

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