The most striking example of point mutation is found in a disease called

The correct option is A

Sickle cell anaemia

The correct option is A

Explanation of the correct option:

1. Sickle cell anemia is an autosomal recessive disease that is caused by a mutation in which the amino acid at the 6th position (glutamine) in the beta chain of hemoglobin is replaced by valine.
2. The major characteristics of the disease are anaemia (less functional RBCs) & a tendency of red blood cells to change shape at low oxygen concentrations. The sickle cells are no longer of use & start breaking down.
3. They tend to jam in the capillaries and small blood vessels and prevent normal blood flow.
4. A whole range of secondary symptoms is possible as a result.
   

Explanation of the incorrect option:

Option B:

Down's syndrome is due to trisomy of chromosome number 21 which is a result of polyploidy.

Option C :

Night blindness is an X-linked recessive disease caused by a mutation in the gene coding for leucin-rich protein.

Option D:

Thalassemia is an example of a deletion mutation in haemoglobin chains.

Final answer: The most striking example of point mutation is found in a disease called sickle cell anaemia.