Prokaryotes have 70S ribosomes, each consisting of a
small (30S) and a large (50S) subunit. Polyribosomes (or
polysomes) are a cluster of ribosomes, bound to a mRNA
molecule in translation during the process of protein synthesis.
It was first discovered and characterized by Jonathan Warner,
Paul Knopf, and Alex Rich in 1963. Polysomes indicate the
synthesis of identical polypeptide in multiple copies.