Polytene chromosome

To increase cell volume, some specialised cells undergo repeated rounds of DNA replication without cell division (endomitosis), forming a giant polytene chromosome.

Related Topics:
Cell - DNA replication - Cell division - Endomitosis

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Polytene chromosomes form when multiple rounds of replication produce chromatids that remain synapsed together in a haploid number of chromosomes. They have charactersitic light and dark banding patterns which can be used to identify chromosomal rearragements and deletions.

Related Topics:
Chromosome - Chromatid - Haploid

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Chromosome puffs are diffuse uncolied regions of the polytene chromosome that are sites of RNA transcription.

Related Topics:
RNA - Transcription

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In addition to increasing the volume of the cells nuclei and causing cell expantion, polytene cells may also have a metabolic advantage as multiple copies of genes permits a high level of gene expression.

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Polytene chromosomes were originally observed in the larval salivary glands of Drosophila melanogaster. They may also occur in protist, plant, and mammalina as well as in cells from other insects.

Related Topics:
Salivary gland - Drosophila melanogaster - Protist - Plant - Mammal - Insect

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