What are Stem Cells?

In genetic terms, stem cells are cells in the embryo that are not specialized. After fertilization, there are two types of cells in the embryo.

Specialized cells:

These are the cells modified with clearly defined instructions or tasks. They are the cells that go on to define set things like taste, hearing, sex, and the like. As they divide and grow, they do NOT change into any kind of cell. They are also called differentiated cells. They are usually modified a few days after fertilization.

Unspecialized cells:

These are cells in the embryo (just after fertilization), usually obtained from human embryos that are a few days old and are leftover from human fertility treatments. These are somewhat ‘generic cells’ and can grow into any of the about 250 cell types in the human body. This type is called Stem Cell. It is also known as undifferentiated cells.

Stem cells also come into two forms or types:

Adult Stem Cell:

These are stem cells that develop into many types of cells.

Embryonic Stem Cell:

These are stem cells that can develop into any kind of cell.

Why are stem cells important?

Scientists use stem cells to treat people with brain diseases by making new brain cells. Some cells are used to rebuild cartilage, bones, and valves in blood vessels. Stem cells technology is fairly new but looks like it will be a great scientific technology in treating many serious cells and tissue diseases including cancer.

Stem cell rejection.

If you remember, we mentioned that our DNA is unique and so are our genes. This means that stem cells from the embryo of another person is very likely to fail if used in treatment for another person. The cells will die because the body will reject them as foreign cells.

However, if the gene or cell is cloned from your own body, there is almost a sure chance that your body will accept it because the DNA is the same.


Stem cells are obtained in embryos (newly fertilized cells). This means that human embryos have to be destroyed to obtain the stem cells for your treatment. Many people of religious faith believe that is not acceptable to destroy embryos, under any circumstance — and is seen as murder.

Discuss with family and friends about Stem Cell technology and how it fits within human life… is it acceptable or not? Why?

Some of our reading resources for the lesson included the following: