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Structure of DNA and RNAEdexcel International A Level Biology: Mind map

What this mind map covers

  • Mononucleotide
  • Polynucleotide
  • Base pairing
  • DNA
  • RNA

Exam questions on Structure of DNA and RNA

  1. A technician extracts DNA from a bacterium and analyses its base composition. The DNA is a double-stranded molecule and 28% of its bases are adenine.
    Explain why the percentage of thymine in this DNA is equal to the percentage of adenine.2 marks
  2. A virologist extracts the genetic material from a newly discovered virus. The material is made of polynucleotide and base analysis gives: adenine 23%, cytosine 27%, guanine 29% and uracil 21%.
    Explain why the base percentages suggest that the molecule is not double-stranded along its whole length.2 marks
  3. One strand of a short section of a DNA molecule has the base sequence TACGGCATT. The section is part of a double-stranded molecule.
    Deduce the base sequence of the complementary strand. Name the bond that holds the two strands together at the bases and state which bases it joins.3 marks
See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).