Solenoid is a structure ofa)Nucelosomal organisation with 10 nm thickn...
The solenoid structure of chromatin is a model for the structure of the 30 nm fibre. It is a secondary chromatin structure which helps to package eukaryotic DNA into the nucleus. So, the correct answer is 'Condensed chromatin fibre with 30nm diameter'.
Solenoid is a structure ofa)Nucelosomal organisation with 10 nm thickn...
The correct answer is option B: Condensed chromatin fibre with 30 nm diameter.
Solenoid is a structural organization of chromatin that refers to the condensed chromatin fiber with a diameter of approximately 30 nm. It is one of the levels of packaging that occurs during the formation of chromosomes. Let's understand this in detail:
1. Chromatin:
Chromatin is a complex of DNA, RNA, and proteins that make up the chromosomes in eukaryotic cells. It is composed of repeating units called nucleosomes.
2. Nucleosomes:
Nucleosomes are the basic units of chromatin and consist of DNA wrapped around a core of histone proteins. Each nucleosome core has about 147 base pairs of DNA wrapped around an octamer of histone proteins.
3. 10 nm Fiber:
The nucleosomes are further organized into a 10 nm fiber by the interaction of histone tails with linker DNA. This fiber is also known as the "beads-on-a-string" structure.
4. Solenoid:
The 10 nm fiber undergoes further compaction to form the solenoid structure. This occurs through the interaction of histone H1 with the linker DNA, causing the nucleosomes to fold into a helical structure. The solenoid structure has a diameter of approximately 30 nm.
5. Higher Levels of Chromatin Organization:
Further compaction of the solenoid structure leads to the formation of higher-order chromatin structures. These include the 30 nm fiber, which is formed by the coiling of multiple solenoid structures. The 30 nm fiber is thought to be the basic unit of chromosome condensation during cell division.
6. Other Levels of Chromatin Organization:
Beyond the 30 nm fiber, chromatin can undergo additional levels of compaction, leading to the formation of highly condensed forms such as the chromatid and the fully condensed chromosome.
In conclusion, the solenoid is a condensed chromatin fiber with a diameter of approximately 30 nm. It is formed by the coiling of nucleosomes into a helical structure and represents one level of chromatin organization.
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