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Giant chromosomes are found in
Giant chromosomes are found in
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The correct option is D Salivary glands of Drosophila
There are chromosomes which are extremely large compared to normal chromosomes. Such, chromosomes, called as giant chromosomes, occur in some animal cells. Two types of giant chromosomes are known:1. Lamp Brush Chromosomes:
These chromosomes occur in the oocytes (germ cells in the ovary) of amphibians and in some insects. They are extremely large synapsed homologous chromosomes which can be seen in the diplotene stage of prophase I in meiosis. They measure about 1500 to 2000 in length. A lampbrush chromosome consists of an axis from which paired loops extend in opposite directions, giving the appearance of a lamp brush. The axis consists of chromomeres (nucleosomes) and interchromomere regions. The loops consist of transcriptionally active DNA which can synthesize large amount of mRNA, necessary for the synthesis of yolk.
2. Polytene Chromosomes
These are giant chromosomes found in the salivary gland cells of the fruit fly, Drosophila. They are many times larger than the normal chromosomes reaching a length of 2000 and are visible even under a compound microscope. The polytene chromosomes appear to contain five long and one short arm radiating from a central point called chromocentre. It is formed by the fusion of centromeres of all the eight chromosomes found in the cell. Of the 6 arms, the short arm represents the fused IV chromosome and the longest represents the fused sex chromosomes. These arms contain numerous chromonemata resulting from repeated replication of DNA, without separation into daughter chromosomes. The arms show characteristic dark bands and light bands. The dark bands are euchromatic regions. Some of the dark bands temporarily swell up and form enlargements called chromosomal puffs or Balbiani rings. These regions contain actively transcribing DNA involved in the synthesis of RNA types.
Thus, the correct answer is option D.
There are chromosomes which are extremely large compared to normal chromosomes. Such, chromosomes, called as giant chromosomes, occur in some animal cells. Two types of giant chromosomes are known:
1. Lamp Brush Chromosomes:
These chromosomes occur in the oocytes (germ cells in the ovary) of amphibians and in some insects. They are extremely large synapsed homologous chromosomes which can be seen in the diplotene stage of prophase I in meiosis. They measure about 1500 to 2000 in length. A lampbrush chromosome consists of an axis from which paired loops extend in opposite directions, giving the appearance of a lamp brush. The axis consists of chromomeres (nucleosomes) and interchromomere regions. The loops consist of transcriptionally active DNA which can synthesize large amount of mRNA, necessary for the synthesis of yolk.
These chromosomes occur in the oocytes (germ cells in the ovary) of amphibians and in some insects. They are extremely large synapsed homologous chromosomes which can be seen in the diplotene stage of prophase I in meiosis. They measure about 1500 to 2000 in length. A lampbrush chromosome consists of an axis from which paired loops extend in opposite directions, giving the appearance of a lamp brush. The axis consists of chromomeres (nucleosomes) and interchromomere regions. The loops consist of transcriptionally active DNA which can synthesize large amount of mRNA, necessary for the synthesis of yolk.
2. Polytene Chromosomes
These are giant chromosomes found in the salivary gland cells of the fruit fly, Drosophila. They are many times larger than the normal chromosomes reaching a length of 2000 and are visible even under a compound microscope. The polytene chromosomes appear to contain five long and one short arm radiating from a central point called chromocentre. It is formed by the fusion of centromeres of all the eight chromosomes found in the cell. Of the 6 arms, the short arm represents the fused IV chromosome and the longest represents the fused sex chromosomes. These arms contain numerous chromonemata resulting from repeated replication of DNA, without separation into daughter chromosomes. The arms show characteristic dark bands and light bands. The dark bands are euchromatic regions. Some of the dark bands temporarily swell up and form enlargements called chromosomal puffs or Balbiani rings. These regions contain actively transcribing DNA involved in the synthesis of RNA types.
These are giant chromosomes found in the salivary gland cells of the fruit fly, Drosophila. They are many times larger than the normal chromosomes reaching a length of 2000 and are visible even under a compound microscope. The polytene chromosomes appear to contain five long and one short arm radiating from a central point called chromocentre. It is formed by the fusion of centromeres of all the eight chromosomes found in the cell. Of the 6 arms, the short arm represents the fused IV chromosome and the longest represents the fused sex chromosomes. These arms contain numerous chromonemata resulting from repeated replication of DNA, without separation into daughter chromosomes. The arms show characteristic dark bands and light bands. The dark bands are euchromatic regions. Some of the dark bands temporarily swell up and form enlargements called chromosomal puffs or Balbiani rings. These regions contain actively transcribing DNA involved in the synthesis of RNA types.
Thus, the correct answer is option D.
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