exam questions

• State what is meant by the term gene (2)

  -       Sequence of bases which code for specific amino acids which make up a specific polypeptide/protein 
• Describe role of TRNA in production of a protein (3) 

  -       TRNA molecules transport amino acids to the ribosome

  -       TRNA molecule has an anticodon that binds to codon on MRNA 

  -       Each TRNA carries a particular amino acid
• Describe how a peptide bond Is formed (2) 

  -       Ribosome holds 2 amino acids in place 

  -       Condensation reaction occurs forming peptide bond 
• Describe the role of tRNA in the production of the protein part of a glycoprotein (2) 

  -       each tRNA brings a specific amino acid to the ribosome 

  -       the tRNA with complementary anticodon binds to Condon on mRNA 

  -       tRNA bonds to ribosome.
•  compare and contrast the process of transcription with the process of DNA replication (4)

  -     both involve the formation of polynucleotides 

  -     both involve DNA helicase for unzipping the DNA

  -     transcription uses RNA nucleotides whereas replication uses DNA 

  -     transcription uses RNA polymerase whereas replication uses DNA polymerase 

  -     transcription produces a single strand of RNA (only copies one strand) whereas replication copies both strands and produces double stranded DNA
• describe how mRNA is synthesised at a template strand of DNA (2) 

  -       RNA nucleotides align with complementary bases on DNA 

  -       RNA nucleotides are joined together by RNA polymerase
• give 3 differences between replication of DNA and transcription of DNA

  -       DNA nucleotides for replication and RNA for transcription 

  -       replication produced another strand of DNA whereas transcription produces an mRNA strand 

  -       DNA polymerase for replication and RNA polymerase for transcription 
• Explain how translation of MRNA synthesises part of a polypeptide molecule (5)

  -       MRNA attaches to a ribosome 

  -       TRNA molecules in the cytoplasm attach to specific amino acids based on their anticodon 

  -       Anti-codons on TRNA line up to codons on the MRNA molecule via complementary base pairing (hydrogen bonds form between the bases)

  -       Ribosome holds amino acids in place so peptide bonds can form between adjacent amino acids
• Describe how transcription is involved in the synthesis of an enzyme (4) 

  -       DNA helicase break hydrogen bonds between bases of DNA, so it unwinds 

  -       Template(anti-sense) strand copied; free nucleotides line up against the strand via complementary base pairing 

  -       Adjacent nucleotides form phosphodiester bonds

  -       Creating an MRNA molecule 

  -       This then leaves nucleus via nucleus pore ready for translation