Mutations - substitution, deletion, insertion, duplication, inversion, translocation

Classification of mutations by their effects on the DNA:

Small-scale mutations
  • Substitutions (base is replaced by one of the other three bases)
    • transition exchanges a purine for a purine (A ↔ G) or a pyrimidine for a pyrimidine, (C ↔ T).
    • transversion exchanges a purine for a pyrimidine or a pyrimidine for a purine (C/T ↔ A/G).
  • Insertions add one or more extra nucleotides into the DNA.
  • Deletions remove one or more nucleotides from the DNA.

Large-scale mutations in chromosomal structure
  • Duplications leading to multiple copies of all chromosomal regions
  • Deletions of large chromosomal regions, leading to loss of the genes within those regions.
  • Translocations: parts of nonhomologous chromosomes change places
  • Chromosomal inversions: reversing the orientation of a chromosomal segment.

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