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:
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.
Figure 2. Macro lesions mutation by mutagens.
Figure 3. Structural changes in chromosomes resulted to macro lesions mutation.
Figure 4. Micronuclei changes resulted to macro lesions mutation.
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