Protein synthesis

• What are the two main stages of protein synthesis?

  Transcription and translation
• What happens during transcription?

  One gene on the DNA is copied into mRNA
• What occurs during translation?

  mRNA joins with a ribosome and tRNA brings amino acids
• What is the role of tRNA in translation?

  Brings specific amino acids to the ribosome
• Where is the mRNA copy of DNA made?

  In the nucleus
• Why is mRNA shorter than DNA?

  It carries only the genetic code for one gene
• What happens to the DNA helix during transcription?

  It unwinds to expose the bases
• What enzyme catalyzes the unwinding of DNA?

  DNA helicase
• What does DNA helicase do during transcription?

  Breaks hydrogen bonds between base pairs
• What aligns opposite the exposed DNA bases during transcription?

  mRNA nucleotides
• What enzyme bonds RNA nucleotides together?

  RNA polymerase
• What is created when one entire gene is copied?

  A new RNA polymer chain
• What happens to mRNA after it is copied?

  It is modified and leaves the nucleus
• How does mRNA exit the nucleus?

  Through nuclear envelope pores
• What must pre-mRNA undergo to become mRNA?

  Modification
• What is the role of splicesomes in pre-mRNA processing?

  They splice out introns, leaving exons
• What are the coding regions of mRNA called?

  Exons
• What is the purpose of translation in protein synthesis?

  To create a polypeptide chain
• Where does modified mRNA go after leaving the nucleus?

  It attaches to a ribosome in the cytoplasm
• At which site does the ribosome attach to mRNA?

  At the start codon
• What does the tRNA molecule do during translation?

  It aligns opposite the mRNA codon
• How does the ribosome facilitate the attachment of tRNA during translation?

  It moves along the mRNA molecule
• What type of bond is formed between amino acids during translation?

  Peptide bond
• What is required for the formation of peptide bonds during translation?

  ATP and an enzyme
• What happens when the ribosome reaches the stop codon?

  Translation ends and the ribosome detaches
• What does the stop codon signify in translation?

  It does not code for an amino acid
• Where does the newly created polypeptide chain go after translation?

  It enters the Golgi body
• What are the main steps of translation?

  1. Modified mRNA attaches to ribosome
  2. Ribosome binds at start codon
  3. tRNA aligns opposite mRNA codon
  4. Ribosome moves along mRNA
  5. Amino acids joined by peptide bonds
  6. Process continues until stop codon
• what are the main steps of transcription?


  1. The DNA helix unwinds to expose the bades to act as template
  2. Only one chain of the DNa acts as a template
  3. DNA replication this unwinding and unzipping is catalyed by DNA helicase.
  4. DNA helicase breaks the hydrogen bonds between the complementary base pairs
  5. Free mRNA nucleotides in the nucleus align opposite exposed complementary base paris.
  6. The enzyme RNA polymerase bonds together the RNA nucleotides(phosphodiester bond)to create a new RNA polymer chain.
  7. Once copied,the mrna is modified and then leaves the nucleus through the nuclear envelope pores
• What is the acronym for transcription?


  H- The DNA helix unwinds to expose the bases to act as a template

  O- Only one chain of the DNA acts as a template

  E- enzyme- DNA helicase unwinding and unzipping and breaks the hydrogen bonds between the complementary base pairs

  M- free MRNA nucleotides In the nucleus align opposite exposed complementary base bases

  E- Enzyme RNA polymerase bonds together the the RNA nucleotides to create a new RNA polymer chain

  -Once the mrna is modified and then leaves the nucleus through the nuclear envelop pores
• Describe how a gene is code for the production of a polypeptide?

  Base sequence in triplets.Determine the order of amino acid sequence in polypeptide