Question

Sickle cell anemia results due to mutation caused by
A. Substitution
B. Insertion
C. Deletion
D. Duplication

Answer 1

Hint: Sickle cell anemia is a disorder of hemoglobin that results in the changed shape of erythrocyte and leads to a low intake of oxygen in the body.

Complete Answer:
- A gene is made of DNA. When a gene is transcribed, it is expressed in the form of protein by process translation. A specific gene process-specific protein.
- If there is any alteration in the gene then this may lead to non-functional protein. This alteration is due to the change in the nucleotide sequence of DNA called a mutation. A mutation causes sickle cell anemia.
- A mutation in the HBB gene causes changes in one of the amino acids which are the building blocks of protein. The mutation in the gene is single base substitution also called a point mutation.
- The point mutation results in the replacement of glutamic acid in valine. The valine is hydrophobic in nature therefore it repeals polar interaction while glutamic acid is hydrophilic and will interact with polar molecules.
- Haemoglobin in RBC has a multisubunit complex and the function of hemoglobin is to transport oxygen in the body. In the sickle cell anemia case, the RBCs appear as shriveled and sickle-shaped which leads to low intake of oxygen in RBC and clotting in the blood vessel, increased heart attack, and another cardiovascular disease.

Hence, the correct answer is option (A) Substitution.

Additional information:
- Various types of mutations are duplication, deletion, insertion, nonsense mutation, frameshift and point mutation.
- In duplication, one piece of DNA is copied one or two times abnormally i.e. a portion of chromosome abnormally gets duplicated, example is Charcot-Marie-Tooth.
- Insertion is caused by addition of a piece of DNA to existing one, example is b- thalassemia and deletion is removal of a piece of DNA from existing one and example is cystic fibrosis.

Note: People with sickle cell anemia are less susceptible to malaria, as the malarial parasite is a mosquito and its life cycle depends on human blood cells.