A cell can be compared to a city. Cities are bustling with activity. People, airplanes, cars, trains, etc... are coming and going to and from it. Structures are being built and others are being torn down. In a sense, proteins can be compared to the people within the city. The proteins cause all the commotion, they make things happen.
As described, all the proteins within a cell go back to that one segment (which we call the specific gene) of the DNA strand. The DNA orchestrates all the commotion caused by proteins similar to the way a conductor leads musicians at a symphony. If the conductor becomes sidetracked and makes a mistake, the harmony can be thrown off. If it is thrown off too much, the music can become chaotic and lose its rhythm.
Fortunately in most cases this doesnt happen. Things run smoothly. And if the rhythm is lost it can usually be corrected.
Back in the molecular world things run the same. A cell can usually correct these subtle mistakes without causing a major catastrophe. However, it is remotely possible that a damaged piece of DNA can cause the cell to die. This will only happen if the damaged segment of DNA codes for a protein that is absolutely essential for the survival of the cell. If this happens, then that specific protein cannot be made. The job that protein performs cannot be completed. Just imagine, a damaged piece of DNA in the cell's nucleus can cause the entire cell to shut down.
Life is fragile, but fortunately not quite that fragile as you might expect. DNA gets damaged often. Luckily, there are cellular components (once again, special proteins) that can fix damaged spots on a piece of DNA. Since there are two strands of DNA these proteins can do a good job of repairing alterations.
When a mutation or alteration occurs on a piece of DNA, there are several different possibilities. The impacts of these possibilities range from minuscule to disastrous.
Possibility #1
The alteration can be fixed and everything continues just like normal.
Possibility #2
The damage occurs on a piece of DNA that isnt ever used by that particular cell (remember, different cells perform different functions too). No single type of cell needs all the information contained within the vast amount of DNA that is present. Likewise, the mistake may not affect the production of the protein at all. Sometimes this occurs even when the mistake is contained within the sequence used to make the protein.
Possibility #3
The protein may either be damaged or not produced at all. This may cause the cell to function inappropriately - it can also lead to the cell's death. In the most disastrous scenario, the cell may become damaged, but still have the ability to divide, forming new, similarly dysfunctional cells just like it.
In most cases, an alteration to a single piece of DNA will not have any far-reaching affects on the cell. But, in instances where the alteration results in the production of a dysfunctional protein and the cell still divides, the alterations are passed onto later generations. This is where serious problems may come into play, even leading to cancer.
Scientists currently believe that several different alterations are responsible for a disaster of this magnitude to ever occur. Additionally, these mutations must probably arise in a special sequence. The odds of all this happening are low, but when it does happen the effects are certainly far-reaching and potentially devastating. |
