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प्रश्न
Describe the structure of a nucleosome.
With the help of a suitable diagram describe the structure of a nucleosome
Describe the structure of a nucleosome, with the help of a well-labelled diagram.
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उत्तर १
In eukaryotes, the packaging of the DNA helix is very complex, as the amount of DNA is very high. When we analyse the structure of the eukaryotic chromosome, we find that it is composed of DNA and proteins. These proteins, known as histones, are basic in nature and are positively charged. Thus, they can easily interact with the negatively charged DNA molecule. The histone proteins first organise to make a unit of eight molecules, which is known as a histone octamer. The negatively charged DNA molecule gets wrapped around this positively charged histone octamer. This complex structure is called a nucleosome. In a typical nucleosome, around 200 base pairs of DNA are present.
उत्तर २
The nucleosomes in chromatin are seen as ‘beads-on-string’. Histones are proteins that are rich in the basic amino acid residues, such as lysines and arginines, which carry the positive charge in their side chains. Eight molecules of histones (two each of H2A, H2B, H3 and H4) get organised to form a histone octamer. DNA is negatively charged, and it is wrapped around the positively charged histone octamer to form the nucleosome. Around the octamer, the DNA molecule is wrapped in 1 and 3/4th turn. The DNA is called core DNA (146 bp), and small segments of DNA linking the octamer are called linker DNA (54 bp). Each nucleosome contains 200 bp of DNA helix.
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संबंधित प्रश्न
Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered throughout the cell. Explain.
Write a note on the packaging of DNA in prokaryotes.
Explain the formation of a nucleosome.
Which of the following is the CORRECT statement with respect to formation of nucleosome?
Which one of the following histone molecule is NOT double in one nucleosome?
The length of DNA segment having 44 base pairs is ______
The net electric charge on DNA and histones is ______.
A stretch of euchromatin has 200 nucleosomes. How many bp will there be in the stretch and what would be the length of the typical euchromatin?
Read the following and answer from given below:
The process of copying genetic information from the template strand of DNA into RNA is called transcription. It is mediated by RNA polymerase. Transcription takes place in the nucleus of eukaryotic cells. In transcription, only a segment of DNA and only one of the strands is copied into RNA.
Monocistronic structural genes are found in which organisms?
Electron Transport System (ETS) is present in a eukaryotic cell in the:
Plasmid has been used as vector because ______.
What is the function of histones in DNA packaging?
What would happen if histones were to be mutated and made rich in acidic amino acids such as aspartic acid and glutamic acid in place of basic amino acids such as lysine and arginine?
Which of the following amino acid residues will constitute the histone core?
What do the 'beads on strings' structure of DNA packaging represent?
Part of chromatins which is densely packed stain darkly and is transcriptionally inactive is called ______.
Distinguish between heterochromatin and euchromatin with reference to staining property and activity.
In a mature, functional mRNA of eukaryotes______.
Histones are enriched with ______.
What is a histone octamer?
Chromatin can be defined as:
How many base pairs are contained in E. coli DNA?
In prokaryotic DNA compaction, the looping step creates how many loop domains?
Which protein introduces negative supercoils in prokaryotic DNA?
What is the role of topoisomerase I in prokaryotic DNA packaging?
What is the role of histone H1 in eukaryotic chromatin?
What is the typical range for linker DNA length between nucleosomes?
