Dictionary > Polytene chromosome

Polytene chromosome

polytene chromosome
(Science: cell biology) 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.


You will also like...

Golgi apparatus (3-D illustration)
Role of Golgi Apparatus & Endoplasmic Reticulum in Protein Synthesis

The endoplasmic reticulum and Golgi apparatus are the organelles involved in the translation step of protein synthesis a..

Lake Wakatipu, New Zealand
New Zealand’s Unique Geographical History

Explore why New Zealand has such unique flora and fauna, and learn why long periods of geographical isolation. This less..

Chemical composition of the body
Chemical Composition of the Body

The body is comprised of different elements with hydrogen, oxygen, carbon, and nitrogen as the major four. This tutorial..

Salmon jumping upstream in the river
Lotic Communities & Animals

A running water environment offers numerous microhabitats for many types of animals. Similar to plants, animals in lotic..

Plant Water Regulation
Plant Water Regulation

Plants need to regulate water in order to stay upright and structurally stable. Find out the different evolutionary adap..

Flowers and tiny fruits of the pomegranate plant
Fruits, Flowers, and Seeds

This tutorial deals with the structure and function of flowers, fruits, and seeds. Also included here are the types of f..