Question

Nucleolus is the site of formation of
(a) Spindle fibers
(b) Ribosomes
(c) Peroxisomes
(d) Chromosomes

Answer 1

These are the macromolecular machines that are responsible for the translation of messenger RNA into proteins. These were first observed by a cell biologist George Emil Palade in 1950, using an electron microscope, as dense particles or granules, and the term "ribosome" was proposed by scientist Richard B. Roberts at the end of 1950.

Complete answer:
The nucleolus is the largest structure in the nucleus of eukaryotic cells. It is a small, dense, and spherical structure present within the nucleus of the cell.
It is a dense region due to the presence of proteins, DNA, and RNA which are formed from specific chromosomal regions called nucleolar organizing regions.
It is best known as the site of transcription and processing of ribosomal RNA and ribosome assembly or ribosome biogenesis.
Ribosome biogenesis is a very tightly regulated process, and it is closely linked to other cellular activities such as growth and division.
As soon as the mature r-proteins are imported into the nucleus and finally the nucleolus. The association and maturation of rRNA and r-proteins result in the formation of the 40S (small) and 60S (large) subunits of the complete ribosome. These are exported through the nuclear pore complexes to the cytoplasm, where they remain free or become associated with the endoplasmic reticulum, forming a rough endoplasmic reticulum
-To prevent wastage of cellular energy and resources when synthesizing non-functional proteins. The cells have an active surveillance system to recognize damaged or defective ribosomes and target them for degradation.
So, the correct answer is 'Ribosomes'.

Note: -In the origin of life, ribosome biogenesis predates cells, and that genes and cells evolved to enhance the reproductive capacity of ribosomes
-If there is a disruption in the assembly or maturation of a mature ribosome, the surveillance system will act as if the subunit is defective.
-Several human ribosomopathy genetic diseases, including inherited bone marrow failure syndromes, which are characterized by a predisposition to cancer and a reduced number of blood cells, are linked with a mutation in ribosome biogenesis. Ribosomal dysregulation may also play a role in muscle wasting.