Virus particle used for gene therapy
organisms consist of cells. Very simple organisms like bacteria
or amoebae consist of one cell only. This cell has to perform all
the tasks necessary to stay alive. Complex organisms like people
consist of billions of cells and hundreds of different cell types.
Different cells perform different tasks. Yet, to a large extend
the cells are autonomous, managing their own growth, energy and
survival just like the amoeba.
cells can function largely independently, because each cell contains
a complete copy of the genome. The best analogy for the genome is
a cookbook, A large collection of recipes (the genes) each describing
how to perform a specific task. Some genes describe tasks that are
essential for every cell in the body, e.g. how to burn fuel for
energy. Other genes describe tasks that are only done by specific
cells. E.g. the genes that describe how to make the light sensitive
machinery are only used in the photoreceptor cells, the light detecting
cells in the retina.
happens if a gene is mutated, in other words if it does not describe
the task properly? If it is a gene of universal importance like
that burning of fuel, the defect will be lethal, because none of
the cells in the body can function properly. But a mutation in a
gene that is only used by specialised cells will often lead to disease.
Sometimes it is quite mild, while for other genes the results can
be more serious. A defect in the gene for rhodopsin, a light sensitive
chemical, means that the photoreceptor cell cannot make rhodopsin;
therefore it cannot react to light, resulting in visual impairment.
This page last modified
18 December, 2012