Question

The condition of sickle cell anaemia is due to
A. Chromosomal mutation
B. Silent mutation
C. Point mutation
D. Frameshift mutation

Answer 1

Hint: The mutation can be characterized as a phenomenon in which the base sequence of the gene [DNA] gets altered and results in change in the chemical structure of the gene leading to a change in the phenotype of the organism. Mutation can be caused by several reasons. The sickle cell anemia is caused by the change in single mismatch of bases.

Complete answer:
Sickle cell anaemia is a genetic blood disorder where RBCs undergo a morphological change and they resemble a sickle shape. This shape reduces the oxygen–carrying capacity thus causing anaemia. It is caused by point mutation.
Point mutation is one type of mutation where a single base is changed resulting in an incorrect amino acid being corporate into a protein.
An abnormal type of haemoglobin called haemoglobin S is found in a person suffering from sickle cell anaemia. This reduces the oxygen–carrying capacity of RBCs.
Due to point mutation glutamic acid is replaced by valine in haemoglobin S. Codon GAA or GAG stands for amino acid glutamic acid. By point mutation where there is a change in a single base i.e., GAA is converted into GUA or GAG is converted into GUG. Both these codons GUA and GUG codes for amino acid Valine. So by point mutation glutamic acid gets replaced by valine in Haemoglobin S which is found in a person suffering from sickle cell anaemia.

So, Option (C) is the correct answer.

Note: Due to the formation of haemoglobin S the oxygen–carrying capacity of RBCs decreases in case of a person suffering from sickle cell anaemia. By point mutation where a single base is changed glutamic acid gets replaced by valine in haemoglobin S.