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प्रश्न
Describe the structure of a nucleosome.
With the help of a suitable diagram describe the structure of a nucleosome
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
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’.
Differentiate between Heterochromatin & Euchromatin.
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 ____________.
A typical nucleosome "bead" is made up of ______.
The additional set of proteins required for packaging of chromatin at higher level are called ______.
The length of DNA can be calculated by ______.
Nucleosome core is made of ______.
Barr body in mammals represents ______.
Histone proteins are ______.
The structure in chromatin seen as ‘beads-on string’ when viewed under electron microscope are called ______.
Find out the wrong statement about heterochromatin.
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:
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?
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’?
Electron Transport System (ETS) is present in a eukaryotic cell in the:
Which process occurs in the regulation of gene expression in prokaryotes but does not occur in the regulation of gene expression in eukaryotes?
Watson and Crick proposed the 'Double Helix' structure of DNA based on data produced by ______
Which one of the following statements about Histones is wrong?
Distinguish between heterochromatin and euchromatin. Which of the two is transcriptionally active?
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 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?
Define the Transfection.
