Answer:
Mutagens may be physical, i.e., ionizing
radiations X-ray,UV rays, gamma rays, DNA reactive chemicals, i.e., hydroxyl
radicals, H2O2, etc., or biological such as virus.
A mutagen can induce mutation by
inducing, a change in the base sequence by insertion, deletion or substitution.
e.g., a single base sequence
substitution at the sixth codon of the -globin gene
changes the codon from GAG to GUG, This results in the substitution of glutamic
acid (Glu) by valine(Val) at the sixth position of the p-globin chain of the
haemoglobin molecule.
The mutant haemoglobin molecule
undergoes polymerization under low oxygen tension causing the change in the
shape of the RBC from biconcave disc to the elongated sickle,i.e., like
structure which is not functional.
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