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1.6 Cell division

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Description

Nature of science:
Serendipity and scientific discoveries—the discovery of cyclins was accidental. (1.4)
Understandings:
  • Mitosis is division of the nucleus into two genetically identical daughter nuclei.
  • Chromosomes condense by supercoiling during mitosis.
  • Cytokinesis occurs after mitosis and is different in plant and animal cells.
  • Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
  • Cyclins are involved in the control of the cell cycle.
  • Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
Applications and skills:
  • Application: The correlation between smoking and incidence of cancers.
  • Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.
  • Skill: Determination of a mitotic index from a micrograph.
Guidance:
  • The sequence of events in the four phases of mitosis should be known.
  • Preparation of temporary mounts of root squashes is recommended but phases in mitosis can also be viewed using permanent slides.
  • To avoid confusion in terminology, teachers are encouraged to refer to the two parts of a chromosome as sister chromatids, while they are attached to each other by a centromere in the early stages of mitosis. From anaphase onwards, when sister chromatids have separated to form individual structures, they should be referred to as chromosomes.
 International-mindedness:
  • Biologists in laboratories throughout the world are researching into the causes and treatment of cancer.
Theory of knowledge:
  • A number of scientific discoveries are claimed to be incidental or serendipitous. To what extent might some of these scientific discoveries be the result of intuition rather than luck?
Utilization:
  • The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy.
Aims:
  • Aim 8: The tobacco industry could be discussed. Suppression of the results of research by tobacco companies into the health effects of smoking tobacco was unethical. Smoking causes considerable social harm, but, with the exception of laws on production and supply in Bhutan, has never been made illegal.

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