The alien lookalike above is actually a picture of an embryo at around six weeks old! A zygote is formed when an egg is fertilised by a sperm. After fertilisation, the zygote starts to divide, it's now called an embryo. All the cells are identical to each other and can become any type of cell. They're embryonic stem cells. These can stay as stem cells or become differentiated (specialised) to become another type of cell such as a muscle cell, red blood cell or a nerve cell. Sometimes you will find adult stem cells among the differentiated cells-these can become differentiated later on.
Function of stem cells
Our chromosomes have thousands of genes that can code for many proteins. We don’t need all of these genetic codes to be active all of the time in our body cells so they're switched off. This way the cell only produces the proteins it needs to function.
Specialised cells produce specific proteins because the genes coding for these proteins are activated or switched on. Embryonic stem cells are able to differentiate into any cell type. This is because any of the genes in their chromosomes are able to be switched on.
Stem cells are important for many reasons. In the embryo, stem cells will develop into the whole body of the organism, including all of the organs such as the heart, lung, skin and other tissues and cells. In some adult tissues, such as bone marrow, adult stem cells are used to replace cells that are lost through normal wear and tear, injury or disease.
Uses of stem cells
The fact that stem cells can undergo cell division and become differentiated to any cell type makes stem cells really interesting to scientists. Potential new treatments to replace cells lost to injury and disease and research may help develop alternatives to organ transplantation as well as testing the effects of new drugs.
Stem cells are not only found in animals but plants too. Let's find out more below.
In plant cells, cell division only happens in certain areas called meristems. Meristems are found at the tips of roots and shoots and in between tissues. The cells in the meristem can divide over and over again to produce non-specialised cells. Some of these cells continue to divide, allowing the plant to grow taller and wider throughout its life.
Other non-specialised cells that are produced at the meristem can develop into any type of specialised plant cell and go on to form different plant tissues, leaves and flowers. This activity contributes to plant growth and development.
Like with human stem cells, plant meristem cells have many uses too. For example, they can be used to produce clones of plants very quickly and economically. Also, plants that have special features such as being disease resistant or frost resistant can be cloned to produce lots of crops, for example for farmers. Another use is to protect rare plant species from extinction by cloning them.
In the following activity, you will describe stem cells and some of their functions.