CHROMOSOMAL DISORDERS

disorders in structure of chromosome
- Due to break in chromosomes some part of chromosome containing important genes is lost
  - DELETION
    - types
      - microscopic deletions
        
        deletion of short arm of chromosome 5
        
        cri-du chat syndrome
        
        short arm of chromosome 4
        
        wolf-hirschhborn syndrome
      - submicroscopic microdeletions
        
        syndrome
        
        prader villi syndrome
        
        angelmann syndrome
        
        wilms tumour
        
        williams
        
        langer giedion
        
        miller dieker
        
        di-george
  - INVERSION
    - single chromosome breaks at two points
      - broken segment rearranges itself
        
        inverting its position
        
        pericentric
        
        paracentric
  - RING CHROMOSOMES
  - ISOCHROMOSOMES
  - TRANSLOCATION
    - reciprocal translocation
      - exchange between two non-homologous chromosomes
        
        after breakage and exchange of fragments
      - examples
        
        translocation of chromosome 11 and 22
    - robertsonian translocation
      - due to break near centromere in two acrocentric chromosomes
        
        short arm of both chromosomes lost
        
        but long arms get fused to form a new chromosome
        
        chromosome number is reduced to 45
        
        examples
        
        chromosome 13 and 14
  - MOSAICISM / CHIMAERISM