Prokaryotic vs Eukaryotic Transcription and Translation

Prokaryotic Transcription

  • Occurs in the cytoplasm.
  • Involves RNA polymerase recognizing -35 and -10 promoter regions to initiate transcription.
  • No additional regulatory elements like promoter proximal or enhancer regions.
  • Shine-Dalgarno sequence (SD Box) present, recognized by ribosomes.
  • Promoter is NOT transcribed, only 5' UTR and 3' UTR are present in mRNA.
  • Transcription directly produces mature mRNA without pre-mRNA.
  • Splicing does not occur due to absence of introns.
  • Transcription termination occurs via a terminator sequence (inverted repeat forming hairpin loop).
  • Transcription and translation can happen simultaneously.

Eukaryotic Transcription

  • Occurs in the nucleus.
  • RNA polymerase recognizes transcription factors bound to the TATA box for initiation.
  • Has promoter proximal and enhancer regions for regulation.
  • Uses 5' cap instead of Shine-Dalgarno sequence.
  • Pre-mRNA undergoes processing, including splicing and adding a 5' cap and poly A tail.
  • Alternative splicing allows multiple mRNA forms from a single gene.
  • Transcription termination occurs at a cleavage site after the 3' UTR.

Prokaryotic Translation

  • Occurs in the cytoplasm concurrent with transcription.
  • Ribosome identifies the SD box and initiates translation at start codon.

Eukaryotic Translation

  • Takes place in cytoplasm, ER, mitochondria, and chloroplasts.
  • Ribosome recognizes 5' cap, scanning the 5' UTR to the AUG start codon.
  • Translation can only occur after transcription and export of mature mRNA.

Complementary Base Pairing

  • Various molecules (DNA, mRNA, rRNA, tRNA) have specific pairing rules in functions like replication and transcription.

Important Sites in DNA

  • Promoter (prokaryotes) - recognized as DNA by RNA polymerase.
  • TATA Box (eukaryotes) - recognized by transcription factors.
  • Translation Start/Stop codons in mRNA relate to tRNA recognition.
  • Terminator sequences in mRNA lead to RNA polymerase dissociation.
  • PolyA signal directs polyA polymerase to add adenine nucleotides to mRNA.