What are the Balbiani rings?
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 are the Balbiani rings and where can they be found?
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?
Chromosome puffs. Electron micrographs of certain puffs, called Balbiani rings, of Chironomus salivary gland polytene chromosomes show the chromatin arranged in loops (Figures 4-42 and 4-43), much like those observed in the amphibian lampbrush chromosomes discussed earlier.
What is the function of polytene chromosomes?
The interbands are involved in the interaction with the active chromatin proteins, nucleosome remodeling, and origin recognition complexes. Their primary functions are: to act as binding sites for RNA pol II, to initiate replication and, to start nucleosome remodeling of short fragments of DNA.
Do humans have polytene chromosomes?
While polytene chromosomes are most frequently found in insects, they are critical in diverse organisms from ciliates to plants to humans, and they play important roles in disease progression.
Where are Balbiani rings present?
(c) Polytene chromosomes was described by Kollar (1882) and first reported by Ballbiani(1881) . They are found in salivary glands of insects (Drosophila) and called as salivary gland chromosomes .
Which is physical basis of heredity?
The genes are found in the chromosomes and it forms the physical basis of heredity. The genes, chromosomes, and the DNA are related to each other; the gene is the segments of DNA that carry the code for a particular protein that involve in the cellular function of the body.
What is a Lampbrush chromosome and where is it found?
Lampbrush chromosome are a special form of chromosome found in the growing oocytes (immature eggs) of most animals, except mammals. Lampbrush chromosomes are clearly visible even in the light microscope, where they are seen to be organized into a series of chromomeres with large chromatin loops extended laterally.
Can you detect the banding pattern of the polytene chromosomes?
The most noticeable feature of polytene chromosome is transverse banding associated with alternation of dense stripes (dark or black bands) and light diffuse areas that encompass alternating less compact gray bands and interbands visible with an electron microscope.
Where is Lampbrush chromosome 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.
What is the function of lampbrush chromosome?
Lampbrush chromosomes are also involved in the production of “masked” mRNAs for early development. The giant granular loops could either be the sites where such mRNAs are packaged or they could be sites where specific alterations of the deoxyribonucleoprotein fiber take place.
Do humans have giant chromosomes?
Polytene chromosomes are formed when the products of multiple rounds of S-phase remain tightly associated to form one supersized chromosome. We also note that polytene chromosomes can form in cells that undergo transient nuclear envelope breakdown without subsequent chromosome separation (Cantero et al.
Where can you find the Balbiani ring gene?
We describe such a system, the Balbiani ring ( BR) genes in polytene cells in the dipteran Chironomus tentans.
Why are the rings on a puff called Balbiani rings?
The chromonemata of puffs give out a series of many loops laterally. As these loops appear as rings, they are called Balbiani rings after the name of the researcher who discovered them. They are formed of DNA, RNA and a few proteins.
How are the Rings of Saturn arranged in the zodiac?
They are arranged in a line parallel to the zodiac, and the middle one (Saturn itself) is about three times the size of the lateral ones.”. He also described the rings as Saturn’s “ears”. In 1612 the Earth passed through the plane of the rings and they became invisible.
Why are puffs and Balbiani rings important to RNA synthesis?
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.