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प्रश्न
Write a note on the packaging of DNA in prokaryotes.
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उत्तर
- In prokaryotes like E. coli, cell size is almost 2-3 µm long.
- They lack a well-organized nucleus i.e. nucleus is without nuclear membrane and nucleolus.
- The nucleoid is a small, circular, highly folded, naked ring of DNA which is 1100 µm (approximately 1.1 mm) long in perimeter, containing about 4.6 million base pairs.
- The nucleoid is to be packaged into a cell that is approximately 2-3 µm long.
- Hence, the negatively charged DNA becomes circular, reducing the size to 350 µm in diameter. This is further reduced to 30 µm in diameter because of folding/looping. 40-50 domains (loops) are formed.
- The formation of loops is assisted by RNA connectors.
- Each domain is further coiled and supercoiled, thereby reducing the size down to 2 µm in diameter.
- This coiling (packaging) is assisted by positively charged HU (Histone like DNA binding proteins) proteins and enzymes like DNA gyrase and DNA topoisomerase I, for maintaining super coiled state.
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संबंधित प्रश्न
The length of DNA can be calculated by ______.
The chromatin is packed to form a solenoid structure of ______ diameter.
Nucleosome core is made of ______.
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?
Plasmid has been used as vector because ______.
Which process occurs in the regulation of gene expression in prokaryotes but does not occur in the regulation of gene expression in eukaryotes?
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?
