Polytene chromosomes
Polytene chromosomes are specific interphase chromosomes consisting of thousands of deoxyribonucleic acid (DNA) strands. For this reason they are very large and display a characteristic band–interband morphology. Polyteny arises in tissues, organs and at developmental stages when there is need for the rapid development of an organ at an unaltered high level of function. Organs containing cells with polytene chromosomes are, as a rule, involved in intense secretory functions accomplished during a short time against a background of rapid growth. Chromosome rearrangements and in situ hybridization on polytene chromosomes allow genes to be mapped to a resolution of a few tens of kilobases. Polytene chromosomes allow a specific narrow region to be dissected out with a micromanipulator and a library of DNA clones to be derived from the region.
Important facts
Polytene chromosomes are specific type of interphase chromosomes consisting of thousands of DNA strands.
Polytene chromosomes have been found in many tissues of the representatives of two orders of insects: Diptera and Collembola, in the macronuclear anlagen of Infusoria, in certain organs and tissues of mammals and also in the cells of the synergids, antipods and endosperm of angiospermous plants.
Polyteny arises in tissues, organs and at developmental stages when there is need for the rapid development of an organ at an unaltered high level of function. Organs containing cells with polytene chromosomes are, as a rule, involved in intense secretory functions accomplished during a short time against a background of rapid growth.
Along the linear axis polytene chromosome have variation in the concentration of the chromatin. Regions of high concentrations are known as chromomeres (bands), and regions with low concentrations are known as interchromomeres (interbands).
The pattern of bands and interbands in each polytene chromosome is specific for the species, and in general is characteristic of that particular chromosome in different tissues or at different developmental stages.
Polytene chromosomes are now considered to be very important objects for the analysis of numerous features of interphase chromosome organization and the genome as a whole.
Keywords: genes; puffs; bands; interbands; heterochromatin
Polytene chromosomes have been found in many tissues of the representatives of two orders of insects: Diptera and Collembola, in the macronuclear anlagen of Infusoria, in certain organs and tissues of mammals and also in the cells of the synergids, antipods and endosperm of angiospermous plants.
Polyteny arises in tissues, organs and at developmental stages when there is need for the rapid development of an organ at an unaltered high level of function. Organs containing cells with polytene chromosomes are, as a rule, involved in intense secretory functions accomplished during a short time against a background of rapid growth.
Along the linear axis polytene chromosome have variation in the concentration of the chromatin. Regions of high concentrations are known as chromomeres (bands), and regions with low concentrations are known as interchromomeres (interbands).
The pattern of bands and interbands in each polytene chromosome is specific for the species, and in general is characteristic of that particular chromosome in different tissues or at different developmental stages.
Polytene chromosomes are now considered to be very important objects for the analysis of numerous features of interphase chromosome organization and the genome as a whole.
Keywords: genes; puffs; bands; interbands; heterochromatin
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