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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
Differentiate between Euchromatin and Heterochromatin.
Repeating units of chromatin are known as ____________.
The additional set of proteins required for packaging of chromatin at higher level are called ______.
Telomere has a unique property of __________.
Nucleosome core is made of ______.
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.
Name the linkage present between the nitrogen base and pentose sugar in DNA.
Which process occurs in the regulation of gene expression in prokaryotes but does not occur in the regulation of gene expression in eukaryotes?
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?
The non-condensed, light stained and transcriptionally active segments of chromosomes are called ______.
