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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.
Attempt any TWO of the following:
With the help of a suitable example illustrate ‘Palindrome’.
Short Answer Question:
Write a short note on DNA packaging in the eukaryotic cell.
Write a note on the packaging of DNA in prokaryotes.
Which of the following is the CORRECT statement with respect to formation of nucleosome?
In prokaryotes, the enzyme RNA polymerase recognizes the promoter by its ______.
The length of DNA can be calculated by ______.
The chromatin is packed to form a solenoid structure of ______ diameter.
Read the following and answer from given below:
In prokaryotes, DNA is circular and present in the cytoplasm but in eukaryotes, DNA is linear and mainly confined to the nucleus. DNA or deoxyribonucleic acid is a long polymer of nucleotides. In 1953, the first correct double-helical structure of DNA was worked out by Watson and Crick. Based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin. It is composed of three components, i.e., A phosphate group, a deoxyribose sugar, and a nitrogenous base. Different forms of DNA are B-DNA, Z-DNA, A-DNA, C-DNA, and D-DNA.
The double helix structure of DNA was proposed by ______
Read the following and answer from given below:
In prokaryotes, DNA is circular and present in the cytoplasm but in eukaryotes, DNA is linear and mainly confined to the nucleus. DNA or deoxyribonucleic acid is a long polymer of nucleotides. In 1953, the first correct double-helical structure of DNA was worked out by Watson and Crick. Based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin. It is composed of three components, i.e., A phosphate group, a deoxyribose sugar, and a nitrogenous base. Different forms of DNA are B-DNA, Z-DNA, A-DNA, C-DNA, and D-DNA.
The double chain of B-DNA is coiled in a helical fashion. The spiral twisting of the B-DNA duplex produces ______
Which one of the following is not considered as part of the endomembrane system?
Which process occurs in the regulation of gene expression in prokaryotes but does not occur in the regulation of gene expression in eukaryotes?
______ are the amino acids of histones.
What is the function of histones in DNA packaging?
Distinguish between heterochromatin and euchromatin. Which of the two is transcriptionally active?
What do the 'beads on strings' structure of DNA packaging represent?
Replication of DNA in eukaryotes is initiated by ______.
Histones are enriched with ______.
Statement I: In prokaryotes, the positively charged DNA is held with some negatively charged proteins in a region called nucleoid.
Statement II: In eukaryotes, the negatively charged DNA is wrapped around the positively charged histone octamer to form nucleosome.
In the light of the above statements, choose the correct answer from the options given below:
What are non-histone chromosomal (NHC) proteins?
In the prokaryotic DNA compaction pathway, what is the diameter of relaxed circular DNA?
What diameter is achieved after the circularisation step in prokaryotic DNA packaging?
Which of the following are core histones that form part of the histone octamer?
How much DNA is wrapped around the histone octamer in a nucleosome?
What is the total DNA content per nucleosome?
What is the diameter of the nucleosome fibre (beads-on-string structure)?
Which locations in the eukaryotic nucleus typically contain heterochromatin?
