Science Week 4

• In this lesson you will understand the structure of DNA and RNA and explain the role of each nucleic acid in protein synthesis
• DNA


  Nucleic acid that stores and transmits genetic information
• DNA Replication


  1. Helicase breaks bonds between bases

  2. Complementary nucleotides added by DNA polymerase

  3. Two new DNA molecules formed with parent and new strands
• Messenger RNA (mRNA)


  Brings information from DNA in nucleus to cytoplasm to make proteins
• Transcription


  1. RNA polymerase binds and opens DNA

  2. RNA polymerase links free RNA nucleotides to complementary DNA strand

  3. RNA molecule breaks away as DNA strands rejoin
• Translation


  1. mRNA binds to ribosome

  2. tRNA anticodon pairs with mRNA start codon

  3. Ribosome slides along mRNA, new tRNA brings amino acid

  4. Amino acids joined by peptide bonds

  5. Polypeptide chain released when ribosome reaches stop codon
• Mutation


  Permanent change in DNA sequence that may affect one gene or whole chromosomes
• Types of Mutation


  • Gene mutation
  • Chromosomal mutation
• Most mutations are harmful, some may be useful