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HSC Biology

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Lesson 18 of 29
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Mutation

How does mutation introduce new alleles into a population?

Inquiry Question

Overview

  • Explain how a range of mutagens operate, including but not limited to:
    • Electromagnetic radiation sources
    • Chemicals
    • Naturally occurring mutagens
  • Compare the causes, processes and effects of different types of mutation, including but not limited to:
    • Point mutation
    • Chromosomal mutation
  • Distinguish between somatic mutations and germ-line mutations and their effect on an organism
  • Assess the significance of ‘coding’ and ‘non-coding’ DNA segments in the process of mutation
  • Investigate the sources of genetic variation relating to the processes of fertilisation, meiosis and mutation
  • Evaluate the effect of mutation, gene flow and genetic drift on the gene pool of populations

Mutations

A mutation is a change in the genetic material of a cell, from a molecule level with a change in DNA nucleotide sequence to an alteration of a whole chromosome.

Spontaneous Mutation

Mutations that occur normally without the effect of a mutagen.

  • DNA replication error during interphase 1 meiosis/mitosis that are NOT repaired or corrected by repair enzymes
  • Unequal crossing over

Induced Mutation

Caused by exposure to an environment agent of mutagen.

  • Electromagnetic radiation
  • Chemical mutagens
  • Naturally occurring mutagens

Cell Replication & Mutation: Background

  • DNA replicates every time a cell undergoes mitosis for growth and repair or meiosis for gamete production. This occurs throughout the life of an organism.
  • Mutations in the copying of this DNA is quote common and cells contain mechanisms to repair these mistakes. If not repaired cancer or cell malfunction may result.
  • DNA repair genes stop the cell cycle while enzymes replace/repair damaged regions. Over 130 genes are responsibly for repairing DNA.
  • Copying errors be be repaired by enzymes such as DNA polymerase that can use the undamaged strand of DNA in the double helix as a template to fix and replace the damaged base sequence.
  • There are two main repair systems: one for removing and replacing a single base-pair mutation, and another for removing long stretches of unwanted, extra base pairs.
  • Once a cell loses its ability to repair damaged DNA, the cell may:
    • Become irreversibly dormant (cannot divide)
    • Become programmed for cell death
    • Become malignant
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