DP Biology (last assessment 2024)
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2.6 Structure of DNA and RNA

Description

Nature of science:
Using models as representation of the real world—Crick and Watson used model making to discover the structure of DNA. (1.10)
Understandings:
  • The nucleic acids DNA and RNA are polymers of nucleotides.
  • DNA differs from RNA in the number of strands present, the base composition and the type of pentose.
  • DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
Applications and skills:
  • Application: Crick and Watson’s elucidation of the structure of DNA using model making.
  • Skill: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.
Guidance:
  • In diagrams of DNA structure, the helical shape does not need to be shown, but the two strands should be shown antiparallel. Adenine should be shown paired with thymine and guanine with cytosine, but the relative lengths of the purine and pyrimidine bases do not need to be recalled, nor the numbers of hydrogen bonds between the base pairs.
 Theory of knowledge:
  • The story of the elucidation of the structure of DNA illustrates that cooperation and collaboration among scientists exists alongside competition between research groups. To what extent is research in secret ‘anti-scientific’? What is the relationship between shared and personal knowledge in the natural sciences?
Utilization:
Syllabus and cross-curricular links:
Biology
Topic 2.2 Water
Topic 3.5 Genetic modification and biotechnology
Topic 7 Nucleic acids

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