7.1 DNA structure

Essential idea:
The structure of DNA is ideally suited to its function.
Understandings: Nature of science:
    Nucleosomes help to supercoil the DNA.

    DNA structure suggested a mechanism for DNA replication.

    DNA polymerases can only add nucleotides to the 3’ end of a primer.

    DNA replication is continuous on the leading strand and discontinuous on the lagging strand.

    DNA replication is carried out by a complex system of enzymes.

    Some regions of DNA do not code for proteins but have other important functions.
    Making careful observations—Rosalind Franklin’s X-ray diffraction provided crucial evidence that DNA is a double helix. (1.8)
Applications : Guidance:
    Rosalind Franklin’s and Maurice Wilkins’ investigation of DNA

    structure by X-ray diffraction.

    Use of nucleotides containing dideoxyribonucleic acid to stop

    DNA replication in preparation of samples for base sequencing.

    Tandem repeats are used in DNA profiling.
    Details of DNA replication differ between prokaryotes and eukaryotes. Only the prokaryotic system is expected.

    The proteins and enzymes involved in DNA replication should include helicase, DNA gyrase, single strand binding proteins, DNA primase and DNA polymerases I and III.

    The regions of DNA that do not code for proteins should be limited to regulators of gene expression, introns, telomeres and genes for tRNAs.
Skill: Theory of Knowledge
    Analysis of results of the Hershey and Chase experiment providing

    evidence that DNA is the genetic material.

    Utilization of molecular visualization software to analyse the association between protein and DNA within a nucleosome.
    Highly repetitive sequences were once classified as “junk DNA” showing a degree of confidence that it had no role. To what extent do the labels and categories used in the pursuit of knowledge affect the knowledge we obtain?

Licence

HL Topic 7 Nucleic acids and proteins Copyright © by Alex Black. All Rights Reserved.

Share This Book