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#polysome

3 public questions tagged with this topic.

Translation Basics

CSIR NET Dec 2006 polysome question answer was

Polysome concept describes multiple ribosomes translating simultaneously on single mRNA, observed as cluster of particles in electron micrographs and heavy fractions in sucrose gradients. The CSIR NET 2006 question tested this definition: string of ribosomes on one mRNA producing multiple copies of same polypeptide, increasing translational efficiency without extra transcription. Polysome profiling assesses translational status: stress or initiation inhibition shifts mRNAs from heavy polysomes to monosomes, indicating global control. Thus polysome reflects coordination of transcription and translation to meet cellular protein demand efficiently.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 7, Polysome definition and translational profiling – CSIR NET context

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Translation Basics

Polysomes increase

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 translationally stalled monosomes, crucial diagnostic for cellular physiology and stress adaptation.

Ref: NCBI Bookshelf, Molecular Biology of the Cell, Section: Polysome function in enhancing translation efficiency

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Translation Basics

Polysome is best described as

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, stress and viral infection. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 7, Polysomes as string of ribosomes on single mRNA

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