Polyteny

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Polyteny

 

the presence in the nucleus of certain somatic cells of giant multifilamentous (polytene) chromosomes, which are hundreds of times larger than normal chromosomes. Polyteny leads to substantial increase in ploidy of the nuclei (up to 32.768N in Chironomus). Polyteny was first described in 1881 by the French cytologist E. Balbiani. Polytene chromosomes are observed in the cells of larvae of a number of Diptera (Chironomus, Drosophila), in Protozoa, and in some plant cells. Polyteny is the result of repeated replications of chromosomes without subsequent divsion of the cell or its nucleus. Giant chromosomes are characterized by specificity of location of the cross-bands, which permits compilation of chromosome maps and study of the functional activities of each band or group of bands.

REFERENCES

Lobashev, M. E. Genetika, 2nd ed. Leningrad, 1967. Swanson, C, T. Merz, and W. Young. Tsitogenetika. Moscow, 1969. (Translated from English.)

M. M. ASLANIAN

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I used conventional methods of polytene chromosome analysis (Shields and Procunier, 1982; Shields, 2013) to determine the sex chromosome constitution of larvae of the S.
It was not possible for us to utilize the first and second instar larval stages for species identification, as they are small, present deep inside the food and their polytene chromosome preparations are not very good.
Polytene chromosome preparations were made from salivary glands of third-instar larvae.
A Polytene Chromosome Analysis of the Anopheles gambiae Species Complex.
Apart from the study of polytene chromosome characteristics, the usefulness of mosquito cytogenetics is mainly to provide a basis for biochemical and molecular investigations.
DNA amplifications, chromatin variations, and polytene chromosomes in differentiating cell of common bread wheat in vitro and root of regenerated plants in vivo.
For example, both chapters on ISH to polytene chromosomes are nearly the same as in the first edition, down to the illustrations and references, and both cover similar material.
dRan is probably in polytene chromosome band 10A7-9.
Out of Texas, thanks to Theophilus Painter, came the discovery of the giant polytene chromosomes in the larval salivary glands, from which grew a huge field of research in population genetics, owing to the fact that about half of all species of Drosophila have polymorphic inversions in at least one chromosome.
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Black flies (Diptera: Simuliidae) provide an interesting case study of the role that chromosome change may play in the diversification process because the morphospecies of classical taxonomy almost always reveals itself as any number of sibling species when polytene chromosomes of larval salivary glands are analyzed (Rothfels, 1988).