Question

What combination of genes of sickle cell anaemia is lethal?

Answer 1

Hint: Sickle cell anemia (SCA) is the most common type to sickle cell disease (SCD). Sickle cell disease is typically inherited from a person’s parent and is a blood disorder. The person with sickle cell disease has a sickle-like shape of the cell.

Complete answer:
The HbS/HbS combination of genes is lethal in sickle cell anaemia. Sickle cell anaemia is inherited from parents and is present from birth. The altered or mutated genes from the mother, father or from both the parents are responsible for the occurrence of disease in an offspring. β-globin gene occurs in the chromosome and is responsible for the formation of haemoglobin. When two abnormal copies of β-globin genes are inherited by a person one from each parent leads to the cause of sickle cell anaemia. Due to the inheritance of abnormal copies of β-globin genes, the shape of red blood cells is sickle or crescent-shaped. Thus, it results in an abnormality in the haemoglobin which is the oxygen carrier protein present in the red blood cells. A person with a single copy of an abnormal gene does not show symptoms of sickle cell anaemia. They are called carriers with the sickle cell trait. Sickle cell anaemia is a type of autosomal recessive disease. If the person receives only one abnormal recessive gene, then the child has 50% of being affected and a 50% chance of being a carrier. If the child inherits both the abnormal recessive gene, then he is 100% affected and possesses the condition of sickle cell anaemia. Due to the presence of homozygous recessive gene HbSHbS, the sickling of red blood cells takes place.

Note: Patients suffering from sickle cell anaemia experience hypoxia as the red blood cells are not capable of carrying oxygen. Abnormal genes of haemoglobin can be detected by haemoglobin electrophoresis. Depending on the exact mutations of the haemoglobin genes, different subtypes exist.