Notes On Mutations And Genetic Code - CBSE Class 12 Biology
Mutation is defined as a change in the genetic code resulting in a loss or gain of a codon. Mutations are triggered by chemical, physical and environmental factors that lead to the addition or deletion or replacement of one or more base pairs of a codon, which, in turn, causes frame-shift mutations and point mutations. In point mutation, only one base is substituted by another base in mRNA template, resulting in a change in the genetic code. Such a change in a single base pair in the gene for the beta globin chain results in a change in amino acid residue glutamate to valine, which ultimately leads to sickle cell anaemia.

In frame-shift mutation, two or more bases are either inserted or deleted from the mRNA template, resulting in the deletion or insertion of a codon. This changes the reading frame only from the point of deletion or insertion. Frame-shift mutation is common among textile workers, often exposed to acridine dyes, which enters their bodies through inhalation or physical contact. These dyes get intercalated or wedged between two adjacent purines, thus increasing the distance between them from 3.4 angstroms to 6.8 angstroms, leading to frame-shift mutation.

Summary

Mutation is defined as a change in the genetic code resulting in a loss or gain of a codon. Mutations are triggered by chemical, physical and environmental factors that lead to the addition or deletion or replacement of one or more base pairs of a codon, which, in turn, causes frame-shift mutations and point mutations. In point mutation, only one base is substituted by another base in mRNA template, resulting in a change in the genetic code. Such a change in a single base pair in the gene for the beta globin chain results in a change in amino acid residue glutamate to valine, which ultimately leads to sickle cell anaemia.

In frame-shift mutation, two or more bases are either inserted or deleted from the mRNA template, resulting in the deletion or insertion of a codon. This changes the reading frame only from the point of deletion or insertion. Frame-shift mutation is common among textile workers, often exposed to acridine dyes, which enters their bodies through inhalation or physical contact. These dyes get intercalated or wedged between two adjacent purines, thus increasing the distance between them from 3.4 angstroms to 6.8 angstroms, leading to frame-shift mutation.

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