A classical example of mutation arise due to change in a single base pair of DNA is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Sickle cell anaemia
Option (1) Sickle cell anaemia — Correct. One base change in the β-globin gene (GAG to GUG) puts valine in place of glutamic acid.
Option (2) Thalassemia — Incorrect. Thalassemia comes from mutation or deletion of globin genes, which makes too little of a globin chain; NCERT does not give it as the classical point mutation.
Option (3) Colour blindness — Incorrect. It is a sex-linked recessive disorder of genes on the X chromosome.
Option (4) Cystic fibrosis — Incorrect. It is an autosomal recessive Mendelian disorder; NCERT does not name it as the classical example of a point mutation.
NCERT Extract:
Mutation – “… Chromosomal aberrations are commonly observed in cancer cells. In addition to the above, mutation also arise due to change in a single base pair of DNA. This is known as point mutation. A classical example of such a mutation is sickle cell anemia.”