SICKLE CELL ANAEMIA

Sickle Cell Anaemia

Sickle Cell Anaemia

Introduction

Sickle Cell Anaemia; first genetic disorder to be characterized at a molecular level, is greatly identified to be occurring as a result of genetic mutation. Mendelian Principle of 'Incomplete Dominance' discovered that this genetic mutation pre-dominantly is inherited. Various experiments were undertaken to identify the defect incited as a result of this mutation that was causing the sickling of the cell and the site of defect was found to be the Haemoglobin molecule. This discovery that resulted in this finding though pointed indirectly to the cause of sickled cells. A more comprehensive procedure called Electrophoresis was subsequently developed and undertaken later, listing the effect of mutation produced as the defect in the haemoglobin molecule; thus providing credibility to the earlier finding.

Sickle Cell Anaemia is an autosomal genetic blood disease in which defected haemoglobin molecule within RBCs; haemoglobin is a protein responsible for the carrying of oxygen, transforms the shape of red blood cells to that of Sickle; crescent. Red blood cells are essentially disc like cells that are involved in carrying oxygen to the bodily organs.

As a result of the point mutation in the B-globin sequence of haemoglobin, RBC's become rigid and sultry blocking the blood vessels, thus preventing the blood flow to central organs and body parts. These RBCs could get ruptured due to increased fragility and tension in the flow of RBCs. When their is a significant decrease in the RBCs due to the rupture and breakdown; called as Haemolysis, Anaemia develops. The blockage in the blood flow could damage organ and render the person on increased risk of contracting any infection.

Prevalence of Disease

Only homozygotes who carry both recessive genes for the Sickle Cell are identified to be suffering from the disease whereas those with one recessive gene; heterozygotes, are called as the carriers. Homozygotes are those who receive haemoglobin mutant genes from both their parents. This is of relevance as we will be discussing the prevalence of Sickle Cell Anaemia, for which Homozygotes will be considered.

Africa is identified as the continent with the highest rate of people suffering from the disease related to Haemoglobinopathies. In US, 1 in 500 African American are found to be suffering from SCA whereas 1 in 100 is the frequency in Africa. Around 300,000 infants are born with Haemoglobin related mutations, with around 200,000 new-borns diagnosed with Sickle Cell Anaemia every year in Africa. This statistics constitute around 66.6% of the new-born population born with Haemoglobinopathies across the world. Sickle Cell Anaemia and Thalassemia are the major diseases resulting from Haemoglobinopathies that are in widespread across the world.

The frequency of carriers in the population determines the population suffering from the disorder. It has been estimated by World Health Organization that around 5% of the population carries genes responsible for Haemoglobinopathies and contract related diseases. The frequency of carriers of Thalassemia is much greater across the world but the cluster and greater frequency of sickle cell genes in certain regions as Africa results ...