Translation or protein synthesis is a process during which the genetic information is translated, following the dictations of the genetic code, into the sequence of amino acids in a polypeptide chain.  The synthesis of all proteins required for the cell is coded on genetic material DNA, which is transcribed to mRNA and translated to proteins. In simple words, Translation is a process in living cells in which the genetic information encoded in messenger RNA(mRNA) called genetic code in the form of a sequence of nucleotide triplets (codons) is translated into a sequence of amino acids in a polypeptide chain during protein synthesis.
10 Differences between translation in Prokaryotes and Eukaryotes
Prokaryotic Translation vs Eukaryotic Translation
Prokaryotic translation
Eukaryotic translation
Coupled Transcription and translation.
It is a continuous process as both transcription and translation occur in cytoplasm. 

It is a discontinuous process as transcription occurs in nucleus while translation on cytoplasm. 
As there is coupled transcription and translation.
Therefore little mRNA processing
Extensive pre mRNA processing

  • Removal of introns & joining of exons
  • Addition of 5’ cap (7methyl guanosine)
  • Addition of poly A tail

mRNA is polycistronic.
  • mRNA with information for many proteins under a single control

mRNA is monocistronic.
  • mRNA with information for only one protein or polypeptide under a single control

It occurs on 70 S Ribosomes
-Consists of 2 subunits, 50S larger subunit and 30S smaller subunit.
It occurs on 80 S Ribosomes.
-Consists of 2 subunits, 60S larger subunit  and 40S smaller subunit
Ribosome small subunit (30S) binds to Shine Dalgarno sequence during translation initiation and further detection of initiation codon
The 43S preinitiation complex (43S PIC) binds to the 5’ 7MeG cap of eukaryotic mRNA.
Moves in 5’---3’ direction and finds AUG codon
Presence of Kozak sequence
(sequence in Eukaryotes with start codon favoring efficient initiation and translation)
Initiator tRNA is formyl methionyl tRNA
(f Met tRNA) which codes for formyl methionine
Initiator tRNA is methionyl tRNA (Met tRNA) that codes for methionine
3 Initiation factors involved:
  • IF1: binds to 30S subunit and prevents premature entry of tRNA to A site
  • IF2-GTP: helps in binding of fMEt tRNA to 30S subunit
  • IF3: binds to 30S subunit and prevents premature binding of 50S subunit and facilitates mRNA binding

Complex process involving ~12 eIFs (Eukaryotic initiation factors)

-eIF1 and eIF1A, eIF2, eIF3, eIF4A, eIF4E, eIF4G, eIF4F, eIF5, eIF5A, eIF5B, eIF6
4 Elongation factors:
  • EF-Tu: bringing aminoacyl-tRNA (aa-tRNA) to A site of the ribosome 
  • EF-Ts: generates active EFTu
  • EF-G: Translocation
  • EF-P: Involved in peptide bond synthesis

4 Elongation factors:
  • eEF1α: bringing aminoacyl-tRNA (aa-tRNA) to A site of the ribosome 
  • eEF1 βϒ : generates active eEF1α:
  • eEF2 :Translocation
  • EEIF5A: Involved in peptide bond synthesis

3 Release factors
  • RF1: Release factor for stop codons UAA &UAG 
  • RF2: Release factor for stop codons UAA &UGA
  • RF3: facilitates binding of RF1 and RF2 to ribosome

Only one release factor
  • eRF1: recognizes all three stop codons

Post translational modifications (PTMs):
  • Relatively low number of PTMs in comparison with eukaryotic proteins.
  • Occurs in cytoplasm
  • Removal of formyl methionine

Extensive post translational modification
  • Primarily Occurs in ER and Golgi before becoming a fully functional protein.

mRNA half life is short( few seconds to minutes) as mRNA is unstable.
mRNA has a half life of few hours to few days; it is quite stable.
It is a faster process, adds up to 17-21 amino acid residues per second.
Comparatively slower. Adds (up to 6-9 amino acid residues per second).
MCQ on translation
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