Toxicology MSDT

PRINCIPLES OF GENETIC TOXICOLOGY

​​Subtopic 2.2: Macro Lesions  (Chromosomal Mutation)


  • Macro lesions are chromosomal mutations with mutagens and are with distinct morphological changes in the phenotype.
  • These morphological changes of chromosomes can be cytologically visible under microscope.
  • Macro lesions are following types:
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2.2a. Numerical changes in chromosomes (Figure 2):
             i) Polyploidy: Duplication of entire set of chromosome to triploid or tetraploid.
             ii) Aneuploidy: Changes of single missing chromosome to monosomy or three copies of a single chromosome to trisomy.

2.2b. Structural changes in chromosomes (Figure 3):
             i) Deletion:  loss of chromosome segment
             ii) Translocation:
                           A segment of one chromosome becomes attached to a non homologous chromosome.
                           It can be one way transfer as simple translocation and two way transfer as reciprocal translocation.
             iii) Inversion: A change in the direction of material along a single chromosome.
             iv) Duplication: Repetition of chromosome segment​

2.2c. Micronuclei changes (Figure 4):
  • Micronuclei (MN) are the damaged chromosome fragments or whole chromosomes that were not incorporated into the cell nucleus and stayed as the extra-nuclear bodies after the cell division.
  • MN can be resulted by the defects of the cell repair machinery and by the accumulation of damaged DNA and chromosomal aberrations.
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Figure 2. Macro lesions mutation by mutagens.
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Figure 3. Structural changes in chromosomes resulted to macro lesions mutation.
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Figure 4. Micronuclei changes resulted to macro lesions mutation.
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