Question

Polysome is formed by
A. Several ribosomes attached to a single mRNA
B. Many ribosomes attached to a strand of endoplasmic reticulum
C. A ribosome with several sub-units
D. Ribosomes attached to each other in a linear arrangement

Answer 1

Hint:- A polyribosome (or polysome or ergosome) is a collection of ribosomes that are attached like “beads on a thread" to an mRNA molecule. In 1963, polysomes were originally coined as "ergosomes" were first invented and were later characterized by Jonathan Warner, Paul M. Knopf, and Alex Rich.

Complete Answer:-A polysome consists of an mRNA molecule complex and two or more ribosomes that work to translate instructions from mRNA into polypeptides. As ribosomes and elongation factors synthesize the encoded polypeptide, polysomes are formed during the elongation process. Several ribosomes travel along the mRNA coding area, forming a polysome. The ability of multiple ribosomes to work on an mRNA molecule describes the cell's restricted mRNA abundance. The composition of the polyribosome varies between prokaryotic polysomes, eukaryotic polysomes, and polysomes attached to the membrane. The function of polysomes can be deduced by a method called polysomal profiling to measure the extent of gene expression. Polysomal Profiling is a process that uses cycloheximide to interrupt translation and a sucrose gradient through centrifugation to isolate the resulting cell sample. Ribosome associated mRNAs migrate quicker than free mRNAs, and mRNAs associated with polysomes migrate faster than mRNAs associated with ribosomes. The calculation of total protein through the gradient discloses many peaks corresponding to mRNA.

Therefore, the correct answer is Option A.

Note:- Each ribosome has two subunits and the two ribosomal subunits dissociate from each other as soon as the translation is terminated, and are re-associated only during the next round of protein synthesis initiation.