Question

can any one explain me the exception of lampbrush chromosomes

Answer 1

-In diplotene stage of meiosis, the yolk-rich oocytes of vertebrates contain the nuclei with many lamp brush-shaped chromosomes of exceptionally large sizes. The lampbrush chromosomes (discovered by Ruckert in 1892) are formed 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.
A lampbrush chromosome contains a main axis whose chromonemal fibres (DNA molecule) gives out lateral loops throughout its length. The loops produce the mRNA molecules of different kinds. In a mature egg, as the chromosome , contracts the lateral loops disappear.

Answer 2

please refer http://www.microbiologyprocedure.com/genetics/chromosomes/special-types-of-chromosomes.htm

Answer 3

Also see
http://what-when-how.com/molecular-biology/lampbrush-chromosomes-molecular-biology/

Answer 4

it is found in oocytes of most animals, except mammals.

Answer 5

i mean why it is called exception will u tell me

Answer 6

maybe because it is a giant chromosome and doesnt come under usual chromosome size dimension

Answer 7

ummmm thats cause in interphase the chromososmes of cells usually decondense and it is not easy at all to visualize them directly .Thats why lamprush chromosomes of vertebrate oozytes and polytene chromosomes found in the gaint secretory cells of insects are exceptional. You can easily visualize them under a light microscope all you need to do is a bit of staining .
Chromosomes during mitosis are usually well packed and we can easily differentiate them under the microsope .But in meiosis , most of the chromosomes are wayyyy more decondensed and not easy to visualize.