Transcription + Translation

• Explain how a mutation can change a protein (enzyme)

  1. Change may create a triplet/codon which codes for a different amino acid than the original
  2. will result in a change of the amino acid sequence
  3. will change the tertiary structure and H/Ionic/Disulfide bonds form in different places
  4. results in a change in the active site of an enzyme
• Describe how mRNA is formed during transcription in eukaryotes (6)

  1. Hydrogen bonds between DNA bases break
  2. Only one strand acts as a template
  3. Free RNA nucleotides align by complimentary base pairing with exposed strand
  4. uracil base pairs with adenine and cytosine with guanine
  5. RNA polymerase joins adjacent free RNA nucleotides
  6. by phosphodiester bonds
  7. Pre-mRNA is spliced to remove introns forming mRNA
• Describe how a polypeptide is formed by translation of mRNA (6)

  1. mRNA attaches to a ribosome
  2. tRNA anticodons bind to complimentary mRNA codons
  3. tRNA brings a specific amino acid
  4. amino acids join by peptide bonds
  5. amino acids join together by use of ATP
  6. tRNA released (after AA joined to polypeptide)
  7. Ribosome moves along mRNA to form polypeptide