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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
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 _______________.
In an octamer of the nucleosome, core DNA consists of ______ base pairs.
Attempt any TWO of the following:
With the help of a suitable example illustrate ‘Palindrome’.
Very Short Answer Question:
Which are the nucleosomal 'core' histones?
Short Answer Question:
Write a short note on DNA packaging in the eukaryotic cell.
Find the odd one out:
Write a note on the packaging of DNA in prokaryotes.
A typical nucleosome "bead" is made up of ______.
The additional set of proteins required for packaging of chromatin at higher level are called ______.
Which one of the following histone molecule is NOT double in one nucleosome?
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 ______
Read the following and answer from given below:
The translation is the process of polymerization of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence bases in the mRNA. The amino acids are joined by a bond called a peptide bond. The ribosome is the site of protein synthesis.
During translation, how many initiation factors are required in eukaryotes for initiation reactions?
Which one of the following cell organelle is considered as ‘Cell within a cell’?
Whittaker placed prokaryotes in:
In the eukaryotic cell cycle, cell fusion experiments show that:
During translation initiation in prokaryotes, a GTP molecule is needed in:
Which one of the following statements about Histones is wrong?
In an experiment, DNA is treated with a compound which tends to place itself amongst the stacks of nitrogenous base pairs. As a result of which, the distance between two consecutive base increases, from 0.34nm to 0.44 nm. Calculate the length of DNA double helix (which has 2 × 109 bp) in the presence of saturating amount of this compound.
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 ______.
Total ATP production during EMP pathway is ______.
Histones are enriched with ______.
