Principles of Inheritance and Variation - Notes | Class 12 | Part 7: Mutation and Pedigree Analysis



It is a sudden heritable change in DNA sequences resulting in changes in the genotype and the phenotype of an organism.

Mutation is 2 types:
  1. Point mutation: The mutation due to change (substitution) in a single base pair of DNA. E.g. sickle cell anaemia.
  2. Frame-shift mutation: It is the deletion or insertion of base pairs resulting in the shifting of DNA sequences.
Loss (deletion) or gain (insertion/ duplication) of DNA segment cause Chromosomal abnormalities (aberrations).

Chromosomal aberrations are seen in cancer cells.

The agents which induce mutation are called mutagens. They include
  • Physical mutagens: UV radiation, α, β, γ rays, X-ray etc.
  • Chemical mutagens: Mustard gas, phenol, formalin etc.

In human, control crosses are not possible. So the study of family history about inheritance is used.

Such an analysis of genetic traits in several generations of a family is called pedigree analysis.

The representation or chart showing family history is called family tree (pedigree).

In human genetics, pedigree study is utilized to trace the inheritance of a specific trait, abnormality or disease.

Symbols used in pedigree analysis

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