GENETIC ENGINEERING: GENETIC DISEASES

Sickle Cell Anaemia: Introduction

Sickle Cell Disease is a group of inherited red blood cell disorders.

Normal red blood cells are round like doughnuts, and they move through small blood tubes in the body to deliver oxygen. Sickle cell anemia occurs when a person inherits two abnormal genes (one from each parent) that cause their red blood cells to change shape. Instead of being flexible and round, these cells are more rigid and curved in the shape of the farm tool known as a sickle - that's where the disease gets its name. When these hard and pointed red cells go through the small blood tube, they clog the flow and break apart. This can cause pain, damage and a low blood count, or anemia.

Hemoglobin, a substance in the red cells, carries oxygen inside the cell. When an abnormal form of hemoglobin (HbS) is produced, the molecules tend to clump together, making red blood cells sticky, stiff, and more fragile, and causing them to form into a curved, sickle shape.

The abnormal hemoglobin is inherited from your parents, who may be carriers with sickle cell trait or parents with sickle cell disease. In other words, you cannot catch it. You are born with the sickle cell hemoglobin and it is present for life. If you inherit only one sickle gene, you have sickle cell trait. If you inherit two sickle cell genes you have sickle cell disease.

It is a hereditary disorder that mostly affects people of African ancestry, but also occurs in other ethnic groups, including people who are of Mediterranean and Middle Eastern descent. More than 70,000 Americans have sickle cell anemia. And about 2 million Americans, and one in 12 African Americans, have sickle cell trait - (this means they carry one gene for the disease, but do not have the disease itself).

Unlike normal red blood cells that last about 4 months in the bloodstream, fragile sickle cells break down after only about 10 to 20 days, which usually causes anemia. Anemia (pronounced: uh-nee-mee-uh) is what happens when the body's number of red blood cells (or amount of hemoglobin) falls below normal. People who are anemic often feel weak and tire more easily.

People with sickle cell anemia can also experience complications from blood circulation and infection-fighting problems. These include a higher risk of certain infections and stroke as well as a condition called acute chest syndrome, which is caused by infection or trapped red blood cells in the lungs.