RAS question
Sickle cell disease is caused by a mutation in which gene?
Correct answer: (C) HBB gene.
Sickle cell disease is caused by variants in the HBB gene, which codes for the beta-globin part of haemoglobin.
Explanation
Sickle cell disease is a haemoglobin disorder, and the decisive gene is HBB. MedlinePlus Genetics states that variants in HBB cause sickle cell disease and that HBB provides instructions for making beta-globin, one part of haemoglobin. The disease is traced to a point mutation in the HBB gene on chromosome 11, where valine replaces glutamic acid at position 6. That change produces haemoglobin S, an abnormal form linked with the sickling of red blood cells. The public-health angle also matters for Indian exams: India launched the National Sickle Cell Anaemia Elimination Mission in 2023 with an elimination target of 2047.
Why the other options are wrong
- (A) HTT is not the haemoglobin beta gene; HTT mutations are linked to Huntington's disease, not sickle cell disease.
- (B) CFTR is not involved in beta-globin or haemoglobin S; CFTR mutations are linked to cystic fibrosis.
- (D) HBA relates to alpha-globin, and HBA mutations are linked to alpha-thalassemia rather than sickle cell disease.
Concept
Single-gene disorders link a disease phenotype to the responsible gene and protein product. This genetics concept recurs in RAS because it connects with public-health programmes such as the National Sickle Cell Anaemia Elimination Mission.