4.2 Protein Synthesis

• If a DNA sequence is TAC TAG what is the mRNA sequence?

  AUG AUC
• What's a difference in the step for translation in a eukaryotic organism compared to a prokaryotic> [2]

  Pre-mRNA has to be spliced to remove introns leaving room for exons, forming mRNA. This then leaves via a nuclear pore and enters the cytoplasm.
• What is the role of RNA polymerase?

  It joins mRNA nucleotides forming phosphodiester bonds between adjacent nucleotides in the backbone.
• What's a common error made in terms of the role of DNA/RNA polymerase and what bonds they form?

  A common error is people saying that they form hydrogen bonds between bases which they DO NOT.
• What's the difference between prokaryotes and eukaryotes in terms of splicing? [2]

  No splicing occurs in prokaryotes as their DNA does not contain introns. Compared to eukaryotes where splicing occurs as they contain introns.
• What is the role of tRNA in translation?

  It carries a specific amino acid to ribosomes, the anticodon is complimentary to the codon resulting in the correct sequence of amino acids along a polypeptide.
• What is the role of ATP in translation?

  It assists in the binding of tRNA to a specific amino acid and the formation of a peptide bond between amino acids
• What is the role of ribosomes in the production of a polypeptide?

  - translation

  mRNA binds to ribosomes with two codons allowing tRNA with anticodons to bind. It catalyses the formation of peptide bonds between amino acids then moves along mRNA to the next codon.
• In a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of the pre-mRNA. Explain why.


  Pre-mRNA contains introns which are removed through the process of splicing to make mRNA