What are Balbiani rings in polytene chromosomes?
Abstract. Balbiani rings are exceptionally large puffs on the polytene chromosomes in the dipteran Chironomus tentans. These puffs are particularly well suited for studies of the structure of active genes and the synthesis and transport of specific RNA-protein (RNP) particles.
What is the function of polytene chromosomes in Drosophila?
Polytene chromosomes are a strongly amplified form of interphase chromosomes, found, for example, in salivary gland cells of Drosophila and Chironomus. They arise through many rounds of DNA replication without subsequent separation of daughter chromatids. The chromatids run through the entire length of a chromosome.
Who first observed polytene chromosome?
Polytene chromosomes were originally observed in the larval salivary glands of Chironomus midges by Édouard-Gérard Balbiani in 1881. Balbiani described the chromosomal puffs among the tangled thread inside the nucleus, and named it “permanent spireme”.
What are puffs in polytene chromosomes?
Puffing is the term that describes structural changes in polytene chromosomes. If one observes polytene chromosomes during the late prepupal stage, different bands appear to be puffed up. For 40 years, this has been understood to be the result of gene activity.
Where Balbiani rings are found?
salivary glands
Balbiani rings are sites of particularly active RNA synthesis on the polytene chromosomes of Chironomids. Three such sites occur on the fourth chromosome in the salivary glands of Chironomus tentans.
Which portion of the chromosome is referred to as the Balbiani ring?
Balbiani rings are sites of particularly active RNA synthesis on the polytene chromosomes of Chironomids. Three such sites occur on the fourth chromosome in the salivary glands of Chironomus tentans.
What does polytene mean?
Definition of polytene : relating to, being, or having chromosomes each of which consists of many strands with the corresponding chromomeres in contact.
Where are Balbiani rings found?
Why are chromosomes called polytene?
As they were discovered in the salivary glands so they are also known as salivary gland chromosomes. They are termed as polytene due to the presence of many chromonemata. They are formed due to repeated duplication of chromosomes without separation. It is known as endomitosis.
Which is largest lampbrush or polytene?
Size. A polytene chromosome is smaller than the lampbrush chromosome, while the lampbrush chromosome is the largest type of chromosomes.
Where lampbrush chromosome is found?
Lampbrush chromosomes (LBCs) are transcriptionally active chromosomes found in the germinal vesicle (GV) of large oocytes of many vertebrate and invertebrate animals and also in the giant single-celled alga Acetabularia. These cells are all in prophase of the first meiotic division.
Do humans have polytene chromosomes?
2006; Wirth et al. 2006). 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 |