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Structure of DNA and RNAEdexcel International A Level Biology: Flashcards

What these 13 flashcards ask

  • What three parts make up a mononucleotide?
  • Which sugar is found in DNA and which in RNA?
  • Which bases are found in DNA?
  • Which bases are found in RNA?
  • What is a phosphodiester bond?
  • What type of reaction joins nucleotides together?
  • How many phosphodiester bonds are in a strand of n nucleotides?
  • Which bases pair together in DNA, and with how many hydrogen bonds?
  • What does adenine pair with in RNA?
  • What is the sugar–phosphate backbone?
  • In double-stranded DNA 30% of bases are adenine. What % are guanine?
  • Why does a region of DNA rich in C–G pairs need more energy to separate?
  • Name two differences between DNA and RNA structure.

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
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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).