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.
What do chromosome puffs indicate?
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. The puffs indicate the site of active genes where mRNA synthesis takes place.
In which of the following ways do polytene chromosomes differ from other chromosomes?
In which of the following ways do polytene chromosomes differ from other chromosomes? Polytene chromosomes are replicated but not separated. … In the formation of nucleosomes, one histone class, H1, is not directly involved, yet it does associate with DNA to form higher level chromosomal structures.
What is the most compacted form in which DNA is found during interphase of the cell cycle?
The most compacted form in which is DNA found during interphase of the cell cycle is nucleosomes coiled into a 30nm fiber. DNA in interphase cells is found in an uncoiled 30nm fiber and is accessible for transcription during interphase through the process of chromatin remodeling.
What is the use of polytene chromosome?
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. They develop from the chromosomes of diploid nuclei by successive duplication of each chromosomal element (chromatid).
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.
What is polytene chromosome write the procedure of squash preparation of Drosophila larvae for polytene chromosome?
4. 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 are polytene chromosomes how are they formed?
Polytene chromosomes develop from the chromosomes of diploid nuclei by successive duplication of each chromosomal element (chromatid) without their segregation. The newly formed chromatids remain associated lengthwise and together form a cable-like structure, referred to as polytene chromosomes.
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.
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.
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.
What is meant by Chromocenter in polytene chromosome?
polytene chromosome chromocenter
A region at which the centric regions of polytene chromosomes are joined together.
When does condensation of chromosomes occur during mitosis?
Prophase is the first stage of mitosis, during which the cell begins to position itself in order to separate the chromatids and divide. During prophase, the nuclear envelope and nucleolus are dissolved and the chromosomes condense.
Which are replicated during interphase?
During interphase, the cell grows and DNA is replicated. During the mitotic phase, the replicated DNA and cytoplasmic contents are separated, and the cell divides.
How does chromosome compaction differ during metaphase and interphase in eukaryotes?
These chromosomes, actually are more condensed in the metaphase than the other stages as these chromosomes are being transported to the opposite poles of the cell in this phase. Conversely, interphase is the stage where these chromosomes are most loosely compacted.