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Understanding Sickle Cell Disease: It's All In Our Genes Many diseases are passed on from parents to their children just like characteristics such as how tall you are or what you look like. Sickle cell disease is an example of an illness that is inherited, we may also call it a genetic disease. In this disease a very important protein inside our red blood cells called hemoglobin is affected. Red blood cells are very important because they pick up oxygen from the lungs and take it all over the body. It is the hemoglobin in red blood cells that actually carries the oxygen. Red blood cells are normally smooth and round. People with sickle cell disease make a different kind of hemoglobin which causes their red blood cells to become hard and sticky. They are also shaped like a sickle, a tool which is used to cut tall grass or wheat. Now you know why this illness is called sickle cell disease.
The reason why sickle-shaped cells make you ill is that these cells sometimes clog up blood vessels and prevent oxygen from getting to the body's tissues. This causes severe pain and can damage the body's tissues. People with sickle cell disease may experience intermittent episodes of severe pain as well as a variety of other problems involving many organs of the body.
Sickle cell disease is passed from parents to their children through their genes. Genes can be thought of as the body's instructions for development. This blueprint tells the body what it should look like or what it should make. Genes come in pairs; we have pairs of genes for the color of our eyes, our blood type, and many other characteristics including the kind of hemoglobin that we make. One gene in each pair comes from our mother and one from our father. Our parents each have 2 genes for hemoglobin but they only pass on one of the 2 genes to each child. Each egg cell from mom has 1 gene for making hemoglobin and each sperm cell from dad has one gene for making hemoglobin. We can represent genes by letters such as "S" for sickle hemoglobin gene and "A" for the regular gene. A person can only get sickle cell disease if he or she receives an "S" gene from each parent. This is because the "A" gene is dominant to the "S" gene. When you have one "A" gene and one "S" gene, or "AS" this is called sickle cell trait and does not cause any illness. One way to think about this situation is that the "A" gene is stronger than the "S" gene and when the two of them are together in a person the "A" gene will always win and prevent the "S" gene from causing problems. In order to better understand these ideas it is helpful to use pictures or symbols to represent the hemoglobin genes.
We can also represent the possible combinations of eggs and sperm that become each child by using the Punnett squares.
When we know the possible combinations of "A" and "S" genes that are produced by parents we can predict the chance of a child being born with sickle cell disease.
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