5. PRINCIPLES OF INHERITANCE AND VARIATION
MUTATION
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:
- Point mutation: The mutation due to change (substitution) in a single base pair of DNA. E.g. sickle cell anaemia.
- Frame-shift mutation: It is the deletion or insertion of base pairs resulting in the shifting of DNA sequences.
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.
PEDIGREE ANALYSIS
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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