Expert: Dana Krempels, Ph.D. - 10/24/2009

Question
   Dear dana,
Good morning There is a great question which confuses us in schools about reasons of multion ( changing genetics ) which happens in human bodies ?
I hope you will answer my question with my greart respect
to you

Best wishes
ahmad

Answer
Dear Ahmad,

I believe you are referring to mutation, any change in the DNA that encodes the instructions for building and "running" any living organism's body.  When a cell reproduces by dividing in two, it must first copy all of its components so that the two resulting cells will have all the necessary parts.  This includes the DNA.  The process of copying the DNA in preparation for cell division is known as DNA replication.  And sometimes when the cell makes a new copy of its own DNA, it can make mistakes.

In many cases, these mistakes are neutral, and do not affect the function of the DNA.  In other cases, the changes are harmful, and can even result in the death of the cell.  But in many cases, the changes can be tolerated and passed on to the next generation of cells without harm, or even by somehow improving the cell's function in its given environment.

Mutations can happen due to random chance, or because of environmental influence of chemicals and other agents.  

In multicellular organisms (including humans), only the mutations that occur in the germ cells--the ones that give rise to sperm and eggs--can be passed on to the next generation.  Mutations that happen in the rest of the body are not passed on to offspring.

This is a very complex topic, and I have given only a very general overview, but I hope it helps introduce the idea of mutations and helps you and your schoolmates to understand.  If you would like more information, I can refer you to some excellent sources for further study.

Good luck,

Dana