Protein synthesis

• How can you describe RNA?

  single stranded
• What monomer makes RNA?

  RNA nucleotides
• What are the 4 RNA bases?

  • adenine complimentary to uracil
  • cytosine complimentary to guanine
• What bonds holds complimentary base pairs together?

  hydrogen bonds
• What bond holds adjacent RNA nucleotides together?

  Phosphodiester bond
• How do mRNA and tRNA differ in size?

  • mRNA is larger than tRNA
  • tRNA has a fixed length whereas the size of mRNA is variable, it depends on the length of the gene
• What is transcription?

  the process by which information in a strand of DNA is copied into a new molecule of mRNA
• What is mRNA?

  messenger RNA
• What is tRNA?

  Transfer RNA
• Explain the process of transcription

  • Helicase uncoils the DNA along the length of one gene
  • Hydrogen bonds break between nucleotide bases
  • One strand of DNA is used, this is called the template strand
  • Free RNA nucleotides complimentary base pair with the template strand
  • Uracil pairs with adenine, Adenine pairs with thymine and cytosine pairs with guanine
  • RNA polymerase catalyses the formation of phosphodiester bonds through condensation reactions that join RNA nucleotides in the pre - mRNA
  • Introns are removed in splicing to produce mRNA
• Explain the process of translation

  • mRNA moves out of the nucleus via a nuclear pore and attaches to a ribosome
  • The ribosome covers 2 codons
  • A specific tRNA molecule brings a specific amino acid
  • The anticodon of the tRNA complimentary base pairs with the mRNA codon
  • Condensation reactions form peptide bonds between amino acids , this requires ATP
  • The ribosome moves along the mRNA and the tRNA detaches
  • This continues until a stop codon is reached
• What type of cell does splicing occur in and why?

  Splicing only occurs in eukaryotic cells as prokaryotic DNA do not have introns
• What is translation?

  The production of polypeptides from the sequence of codons carried by mRNA
• Describe 2  differences between the structure of a tRNA molecule and the structure of an mRNA molecule

  1. tRNA has hydrogen bonds whereas mRNA does not
  2. tRNA has anticodon, mRNA has codon