3 public questions tagged with this topic.
Prokaryotic ribosomes are approximately 15 nm by 20 nm, are associated with the plasma membrane and contain 50S and 30S subunits, forming a 70S ribosome. Several ribosomes on one mRNA constitute a polysome.
Ref: NCERT Class 11 Biology Chapter 8: Cell: The Unit of Life Prokaryotic Cell - Structure and Components
Polysome formation substantially increases translational efficiency by enabling parallel synthesis of many polypeptide copies from single mRNA transcript. After first ribosome initiates and moves downstream, subsequent ribosomes load at 5' cap and begin elongation, creating queue. This multiplies output per mRNA lifetime, economizes transcriptional resources, allows rapid bursts of protein production upon stimulus. Regulation of polysome assembly via initiation factors controls global protein synthesis. Polysome profiling discriminates highly translated mRNAs in dense fractions versus translat
Ref: NCBI Bookshelf, Molecular Biology of the Cell, Section: Polysome function in enhancing translation efficiency
Polysome, also called polyribosome, describes configuration where multiple ribosomes simultaneously translate same mRNA strand arranged like beads on string visible in electron micrographs. Each ribosome decodes 5' to 3' direction synthesizing independent polypeptide chain, spaced roughly 80 nucleotides apart. Polysomes increase protein yield per transcription event without requiring additional mRNAs. In sucrose gradient profiles, heavy polysome fractions indicate active translation, light monosome fractions indicate repression, enabling studies of translational control during differentiation,
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 7, Polysomes as string of ribosomes on single mRNA
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