What is polytene chromosome explain in detail?
What is polytene chromosome explain in detail?
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.
Is polytene chromosome present in human?
Polytene chromosome is found in a diverse set of insects, plants, animals, and unicellular organisms (Table 1). Polytenes can also result pathologically from perturbations in cell cycle regulation….Table 1.
| Type | Animals |
|---|---|
| Subtype | Mammals |
| Species | Human |
| Cell type | Trophoblast giant cell |
What genetic process is occurring in a puff of polytene chromosome?
These puffs and Balbiani rings are sites of active RNA synthesis; therefore, polytene chromosomes and more specifically puffs and Balbiani rings are excellent tools to study the induction and process of transcription.
Which stain is used in polytene chromosome?
Acetic orcein staining
Acetic orcein staining of polytene chromosomes was introduced in 1941 shortly after the initial studies on aceto-carmine-stained chromosomes by Bridges (2) and has remained a standard method of preparation.
How are polytene chromosomes formed in the cell?
Polytene chromosomes are formed due to endoduplication, duplication without separation and replication of DNA without cell division Endoduplication refers to the replication of DNA during the S phase (of the cell cycle) without the completion of cytokinesis.
What causes the swelling of the polytene chromosome?
The bands of polytene chromosomes become enlarged at certain times to form swellings called puffs. The formation of puffs is called puffing. In the regions of puffs, the chromonemata uncoil and open out to form many loops. The puffing is caused by the uncoiling of individual chromomeres in a band.
Where are the PUFs located on a polytene chromosome?
During larval development, specific areas on polytene chromosomes become uncoiled, forming localized regions called ‘pufs’. Puffs represent regions of active RNA synthesis (transcription). In the puff individual fibres remain continuous across the puff and they become extended as short lateral loops (Bahr, 1954).
How are the inter bands of a polytene chromosome stained?
The dark bands are darkly stained and the inter bands are lightly stained with nuclear stains. The dark bands contain more DNA and less RNA. The interbands contain more RNA and less DNA. The amount of DNA in interbands ranges from 0.8 – 25%. The bands of polytene chromosomes become enlarged at certain times to form swellings called puffs.