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.