gene expresiion

• transcription

  IN NUCLEUS. primary transcript produced
• splicing

  During splicing introns are removed from the primary mRNA transcript and the exons or coding regions remain and are spliced together.

  The exons when spliced together form a mature mRNA transcript

  mature mRNA transcript leaves nucleus through a nuclear pore
• dna -> (TRANSCRIPTION) -> primary RNA -> (SPLICING) mature mRNA (TRANSLATION) -> protein
• translation

  IN RIBOSOME. mRNA decoded by ribosome to produce polypeptide
• translation 


  in ribosome -mRNA molecule travels through the cytoplasm and attaches to the ribosome

  • tRNA molecules transport specific amino acids to the ribosome
  • each mRNA codon codes for a specific amino acid
  • the first codon is a start codon - beginning of translation
  • the codons and anticodons match up and form complementary base pairs
  • peptide bonds form between adjacent amino acids to form a polypeptide
  • used tRNA molecules exit the ribosome and collect another specific amino acid
  • the last codon off an mRNA molecule is a stop codon
• transcription


  making mRNA in nucleus

  • RNA polymerase moves along the DNA unwinding the strand
  • DNA molecule unzipped, breaking hydrogen bonds between bases separating DNA into 2 strands
  • RNA polymerase synthesises primary mRNA transcript from RNA by complementary base pairing - contains exons and introns
  • during splicing, introns are removed and exons remain, they get spliced together to form mature mRNA transcript
• how are different proteins produced in alternative splicing

  Different introns are removed from the primary transcript