There are some genes which are constantly being translated to proteins. Such as proteins required for energy production, passage of large molecules through the membrane, repair and maintenance of the cell.
These genes are called ‘housekeeping’ genes.
However there are some genes which are only required by the cell during specific times of the day or during its life span. These genes must be regulated.
For example, plants will only express genes required for photosynthesis when there is light present. Other genes may only be switched on when there is a temperature change or specific ions are present in the body.
So, every cell in your body from nerve cells to muscle cells, contain the exact same DNA, but they look and act completely different?
This is achieved through Gene regulation. Gene regulation allows a cell to ‘turn on’ some genes and ‘turn off’ other genes, thus regulating what proteins are formed by the cell.
Another example is E.coli. This bacteria lives in our gut, living off what ever food we eat.
There are time where this bacteria must have enzymes present to break down proteins or fats or carbohydrates.
In an effort to conserve energy they can’t be producing proteins they don’t need. At times these bacteria can go from having no enzymes which can break down Fructose, to 50% of their body weight being enzymes capable of digesting fructose.
Meaning they ‘regulate’ the production of these enzymes.
Before we start discussing how genes are turned off and on, we need to discuss a few basic terms.
Regulatory Gene
Regulatory protein
Regulatory sequence
To regulate or Not to regulate
A regulatory gene, codes for a regulatory protein. This protein attaches its self to a regulatory sequence.
A regulatory sequence is a small piece of DNA which sits just above the gene you want to transcribe (an example is a promoter or TATA box).
The regulatory protein attracts RNA polymerase, signalling it to transcribe the gene.
Observe the animation to the right
Scroll over each word to see where it lies on the DNA. Then click the start button
Prokaryotes such as bacteria have slightly different gene regulatory machinery.
