Sunday, July 26, 2020

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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