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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
How are the following formed and involved in DNA packaging in a nucleus of a cell?
(ii) Nucleosome
(iii) Chromatin
Differentiate between Euchromatin and Heterochromatin.
Name the transcriptionally active region of chromatin in a nucleus.
The number of adenine molecules in a given DNA segment is 25 and the number of cytosine molecules is 45, the total number of nucleotides in the segment is _______________.
Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered throughout the cell. Explain.
Find the odd one out:
Differentiate between Heterochromatin & Euchromatin.
Draw a neat and labelled diagram of the Nucleosome.
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 ______.
A typical nucleosome "bead" is made up of ______.
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 ______.
Which of the following is correct about mature RNA in eukaryotes?
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 ______
Flagella are present both in prokaryotic and eukaryotic cells, however, they differ in:
Which one of the following cell organelle is considered as ‘Cell within a cell’?
Histones are rich in ______.
Which process occurs in the regulation of gene expression in prokaryotes but does not occur in the regulation of gene expression in eukaryotes?
During translation initiation in prokaryotes, a GTP molecule is needed in:
The most abundant prokaryotes helpful to human in making curd from milk and in the production of antibiotics are the ones categorised as ______ .
In a mature, functional mRNA of eukaryotes______.
Define the Transfection.
Nucleosomes are the repeating units of chromatin the part between adjacent nucleosomes is called ______ .
