Further, the polytene chromosome located within the larval salivary glands of Drosophila, provide scientists the unique ability to directly visualize structural changes that result from the epigenetic modifications of chromatin [10,11].
Where is polytene chromosome found?
Polytene chromosomes are usually found at the interphase nuclei of some tissue of the larvae of flies. Polytene chromosomes are considered to be very useful for the analysis of many facets of eukaryotic interphase chromosome organization and the genome as a whole.
How many polytene chromosomes are found in Drosophila?
Drosophila melanogaster has four chromosomes, three autosomes and a pair of sex chromosomes. The reference system proposed by Bridges divides the limbs of salivary gland chromosomes into 102 sections called “divisions” designated by number from 1 to 102.
Which stain is used to observe polytene chromosomes?
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 prepared?
Polytene chromosome squash preparation: Rinse larvae with water and transfer to PBS in a tissue culture dish for dissection. Grasp the tip of the mouth hooks with one pair of forceps, hold the body about 2/3 of the way down with the other pair, and pull on the mouth hooks so the salivary glands are exposed.
What is salivary chromosome?
Definition of salivary chromosome
: one of the very large polytene chromosomal strands made up of many chromatids that are typical of the salivary gland cells of various insects.
Which chromosome is Telocentric within a polytene chromosome?
They show somatic synapsis. The centromeres of all 8 chromosomes (2n=8) are together in a structure called the chromocenter, therefore they appear to have 5 long arms and one short one (chromosome 1 is the X and is telocentric, chromosome 2 and 3 are metacentric, and chromosome 4 is tiny and is telocentric).
What is salivary gland in Drosophila?
Drosophila salivary glands consist of two major cell types: secretory cells and duct cells. Secretory cells are columnar epithelial cells that synthesize and secrete high levels of protein. Duct cells are cuboidal epithelial cells that form the simple tubes connecting the secretory cells to the larval mouth.
When was the polytene chromosome first discovered and in which species?
Polytene chromosomes were first discovered in the 1880s in insects (Balbiani 1881). One of the earliest published examples of polytene chromosomes is of Chironimus salivary gland chromosomes found in Walther Flemming’s 1882 book, Zellsubstanz, Kern, und Zelltheilung (Flemming 1882).
What is Lampbrush and polytene chromosome?
The main difference between polytene and lampbrush chromosome is that polytene chromosomes occur in the salivary glands and other tissues of insects whereas lampbrush chromosomes occur in the oocytes of vertebrates except for mammals and some invertebrates.
Why salivary gland chromosomes are also called polytene chromosome?
In insects, polytene chromosomes are commonly found in the salivary glands; they are also referred to as “salivary gland chromosomes”. The large size of the chromosome is due to the presence of many longitudinal strands called chromonemata; hence the name polytene (many stranded).
Do polytene chromosomes show somatic pairing?
The salivary gland chromosome is also known as polytene chromosomes. … These chromosomes undergo somatic pairing to form identical chromosomes which are joined along their length to one another.
Why is acetic acid used in polytene chromosomes?
Acetic acid is another popular non-coagulative fixative component known for its swelling affect on tissues  that in the case of polytene chromosome squashes helps to accommodate stretching of the chromatin in the interband regions .