Advertisements
Advertisements
Question
Write a note on the packaging of DNA in prokaryotes.
Solution
- 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.
APPEARS IN
RELATED QUESTIONS
Explain the role of histones in forming a nucleosome.
Repeating units of chromatin are known as ____________.
The octamer of histone protein is made of ______.
Which one of the following histone molecule is NOT double in one nucleosome?
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.
In the eukaryotic cell cycle, cell fusion experiments show that:
______ are the amino acids of histones.
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 most abundant prokaryotes helpful to human in making curd from milk and in the production of antibiotics are the ones categorised as ______ .
Part of chromatins which is densely packed stain darkly and is transcriptionally inactive is called ______.
