Question

Nucleolus is formed by
A. Mitochondria
B. Nucleus and ribosome
C. Primary constriction
D. Secondary constriction.

Answer 1

Hint: The nucleolus is a tiny, concentrated and round structure found in the nucleus of the cell that is shown during the time of the interphase of the cell division under the microscope. Secondary constrictions mark the locations at which the nucleoli are assembled.

Complete step by step answer:
To answer this question, first, we need to know about the nucleolus. The nucleolus is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis. Nucleoli also participate in the formation of signal recognition particles and function in the response of cells to stress. Nucleoli are made of proteins, DNA and RNA and form around a specific part of chromosome known as nucleolar structural areas.
Now, let us find the solution from the options.
Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP).
Ribosomes are huge components of protein and ribonucleic acid (RNA) cause for protein formation by the process of DNA transcription.
Primary constriction also known as centromere displays positive Feulgen reaction specify the availability of DNA.
The nucleolus is produced by the secondary constriction. The nucleolus is the vast structure found in the nucleus of eukaryotic cells where it mainly functions as the region of ribosome formation and construction. Some other vital functions of nucleoli like the construction of signal specifying components and performing a role in the response of the cell to stress. Nucleoli are composed of proteins and RNA and develop enclosing particular chromosomal areas.

So, the correct answer is “Option D”.

Note:
Three major components of the nucleolus are specified: the DFC (dense fibrillar component), GC (granular component) and FC (fibrillar center). Transcription of the rDNA occurs in the FC. The DFC consists of the protein fibrillarin, which is important in rRNA processing. The GC contains the protein nucleophosmin that is also associated with the ribosome biogenesis.