What Causes Sickle Cell Anemia?
Sickle cell anemia is an inherited disease. People
who have the disease inherit two copies of the sickle cell geneone from
each parent.
The sickle cell gene causes the body to make
abnormal hemoglobin. Hemoglobin is the iron-rich protein that gives blood its
red color and carries oxygen from the lungs to the rest of the body.
In sickle cell anemia, the hemoglobin sticks
together when it delivers oxygen to the bodys tissues. These clumps of
hemoglobin are like liquid fibers. They cause the red blood cells to become
stiff and shaped like a sickle, or C. The sickled red blood cells
tend to stick together and get caught in the blood vessels. (Other cells also
may play a role in this process.)
Two copies of the sickle cell gene are needed for
the body to make the abnormal hemoglobin found in sickle cell anemia.
Sickle Cell Trait
If you inherit only one copy of the sickle cell gene
(from one parent), you will not have sickle cell anemia. Instead, you will have
sickle cell trait.
People who have sickle cell trait usually have no
symptoms and lead normal lives. However, they can pass the sickle cell gene to
their children.
The following image shows how two parents who have
sickle cell trait can pass the sickle cell gene to their children.
Example of an Inheritance Pattern for Sickle Cell
Trait
The image shows how sickle cell
genes are inherited. A person inherits two copies of the hemoglobin
geneone from each parent. A normal gene will make normal hemoglobin (A).
An abnormal (sickle cell) gene will make abnormal hemoglobin (S).
When each parent has a normal gene
and an abnormal gene, each child has: a 25 percent chance of inheriting two
normal genes; a 50 percent chance of inheriting one normal gene and one
abnormal gene; and a 25 percent chance of inheriting two abnormal genes.
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