Genes are the blueprint of our
bodies, a blueprint that creates the variety of proteins essential to any
organisms survival. These proteins which are used in countless ways by our bodies
are produced by genetic sequences, i.e. our genes, as described in the cell
biology section, protein synthesis.
Utilization
of Genetic Information
All cells have originated from the
single zygote cell that formed it, and therefore
possess all the genetic information that was held in that zygote. This means
that an organism could be cloned from the genetic information in the nucleus of
one cell, regardless of the volume of cells that make the organism (be it one
or billions).
However, this brings about the
following question, how can cells become differentiated and specialised to
perform a particular function if they are all the same? The answer to this is
each cell performing its unique role has some of its genes 'switched on'
and some 'switched off'.
In light of this, the cells in our
body still contain the same genetic information, though only a partial amount
of this information is being used in any one cell.
Switched
On and Switched Off
Some genes are permanently switched
on, because they contain the blueprint for vital metabolites (enzymes required
for respiration etc). However, since cells become specialised in multi-cellular
organisms such as ourselves, some genes become switched off because they are no
longer required to be functional in that particular cell or tissue.
For instance, insulin is produced in pancreas cells, which must have the gene that
codes for insulin switched on, and perhaps other genes that are un-related to
the role of the pancreas can be switched off.
Some other genes that will be
functional during specialisation determine the physical characteristics of the
cell, i.e. long and smooth for a muscle cell or indented like a goblet cell
Skin Colour
Skin colour is an excellent example
of genetic control at work. Skin colour depends on the degree of melanin found in skin cells. The amount of melanin is
pre-determined by the genetic blueprint of some genes in each cell. To be
exact, there are two genes that control the production of melanin, each of
which has a dominant and recessive expression.
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