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प्रश्न
Describe the structure of a nucleosome.
With the help of a suitable diagram describe the structure of a nucleosome
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उत्तर १
In eukaryotes, the packaging of DNA helix is very complex, as the amount of DNA is very high. When we analyze the structure of 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 histone octamer. The negatively charged DNA molecule gets wrapped around this positively charged histone octamer. This complex structure is called 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 like 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 organized to form histone octamer. DNA is negatively charged and it is wrapped around the positively charged histone octamer to form the nucleosome. Around the octamer, DNA molecule is wrapped as 1 and 3/4th turn. The DNA is called core DNA (146 bp) and small segments of DNA linking 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.
Explain the role of histones in forming a nucleosome.
In an octamer of the nucleosome, core DNA consists of ______ base pairs.
AUG codon gives ________ & ________ amino acids in prokaryotes & Eukaryotes respectively.
Write a note on the packaging of DNA in Eukaryotes.
Explain the formation of a nucleosome.
Which of the following is the CORRECT statement with respect to formation of nucleosome?
Repeating units of chromatin are known as ____________.
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.
The net electric charge on DNA and histones is ______.
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 ______
Flagella are present both in prokaryotic and eukaryotic cells, however, they differ in:
Electron Transport System (ETS) is present in a eukaryotic cell in the:
During translation initiation in prokaryotes, a GTP molecule is needed in:
______ are the amino acids of histones.
Which one of the following statements about Histones is wrong?
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 ______.
Distinguish between heterochromatin and euchromatin with reference to staining property and activity.
