Medical Definition of Polytene chromosome

1. Giant chromosomes produced by the successive replication of homologous pairs of chromosomes, joined together (synapsed) without chromosome separation or nuclear division. They thus consist of many up to 1000) identical chromosomes (strictly chromatids) running parallel and in strict register. The chromosomes remain visible during interphase and are found in some ciliates, ovule cells in angiosperms and in larval Dipteran tissue. The best known polytene chromosomes are those of the salivary gland of the larvae of Drosophila melanogaster which appear as a series of dense bands interspersed by light interbands, in a pattern characteristic for each chromosome. The bands, of which there are about 5,000 in Drosophila melanogaster, contain most of the DNA (ca 95%) of the chromosomes and each band roughly represents one gene. The banding pattern of polytene chromosomes provides a visible map to compare with the linkage map determined by genetic studies. Some segments of polytene chromosome show chromosome puffs, areas of high transcription. This entry appears with permission from the Dictionary of Cell and Molecular Biology (11 Mar 2008)

Lexicographical Neighbors of Polytene Chromosome

polysyllables
polysymbrachydactyly
polysynaptic
polysynaptic
polysyndactyly
polysyndeton
polysyndetons
polysynthetic
polysynthetic
polytechnic
polytechnics
polytechnic institute
polytendinitis
polytene
polytene
polytene chromosome (current term)
polytenies
polytenisation
polytenization
polyteny
polyteny
polyterpenes
polytetrafluoroethylene
polytetrafluoroethylene
polythalamia
polythalamous
polytheism
polytheisms
polytheist
polytheistic

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