13
Question
Select the correct option with respect to coiling of the genetic material in eukaryotic cells.
Select the correct option with respect to coiling of the genetic material in eukaryotic cells.
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Solution
The correct option is B Chromatin→ solenoid→ supercoil→ chromatid
DNA is the genetic material, eukaryotes store their DNA in the well enclosed body called the nucleus. Each human cell contains approximately 2 meters of DNA if stretched end-to-end; yet the nucleus of a human cell, which contains the DNA, is only about 6 μm in diameter. Hence, the diameter or the volume of the nucleus to enclose a long DNA thread is insufficient. So, in order to pack DNA properly inside the nucleus it is wrapped around histone proteins.
The 8 histone molecules 2x (H2A, H2B, H3, and H4) called histone octamer, around which DNA wraps up, forms a nucleosome. Nucleosomes are stable due to the presence of hydrogen bonding and can be seen as beads on thread inside the nucleus when viewed under the electron microscope. These thread-like beaded structures are known as chromatin because they are seen as coloured bodies when stained with 10 nm diameter.
The chromatin further coils, finally forming a solenoid with a 30 nm structure. This is more condensed than the chromatin.
This condenses even further to form chromatin loops which are 300 nm in diameter, called the supercoil. The supercoil condenses further to form a chromatid that has a diameter of 700 nm.
Hence, the proper sequence is chromatin→ solenoid→ supercoil→ chromatid
DNA is the genetic material, eukaryotes store their DNA in the well enclosed body called the nucleus. Each human cell contains approximately 2 meters of DNA if stretched end-to-end; yet the nucleus of a human cell, which contains the DNA, is only about 6 μm in diameter. Hence, the diameter or the volume of the nucleus to enclose a long DNA thread is insufficient. So, in order to pack DNA properly inside the nucleus it is wrapped around histone proteins.
The 8 histone molecules 2x (H2A, H2B, H3, and H4) called histone octamer, around which DNA wraps up, forms a nucleosome. Nucleosomes are stable due to the presence of hydrogen bonding and can be seen as beads on thread inside the nucleus when viewed under the electron microscope. These thread-like beaded structures are known as chromatin because they are seen as coloured bodies when stained with 10 nm diameter.
The chromatin further coils, finally forming a solenoid with a 30 nm structure. This is more condensed than the chromatin.
This condenses even further to form chromatin loops which are 300 nm in diameter, called the supercoil. The supercoil condenses further to form a chromatid that has a diameter of 700 nm.
Hence, the proper sequence is chromatin→ solenoid→ supercoil→ chromatid
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