How does DNA work?

Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the development and function of living things.

The main role of DNA in the cell is the long-term storage of information. It is often compared to a blueprint.

The DNA can change during our life : here you can read about this: http://en.wikipedia.org/wiki/Dna#Chemical_modifications

IF you meant to ask about mutations that are changes to the base pair sequence of genetic material (either DNA or RNA). Mutations can be caused by copying errors in the genetic material during cell division and by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately under cellular control during processes such as meiosis or hypermutation.

http://en.wikipedia.org/wiki/Mutation

Mutations create variation in the gene pool, and the less favorable (or deleterious) mutations are removed from the gene pool by natural selection, while more favorable (beneficial or advantageous) ones tend to accumulate, resulting in evolutionary change.

many thanks.

The DNA is a reservoir of information from the development of the fetus to specific proteins and enzymes that the body needs every day.
A change in the DNA sequence is called a mutation.
This mutation can cause a creation of the wrong enzyme or protein end the cell will not function normally or even die.

A mutation in a body cell (skin cell, liver cell et cetera, but not sex cells) can happen at an early stage of the fetus, and then we will see the problem in a larg area of the body, and it can happen during our lifetime and then we will see the problem in a small area in the body.
In any case, the mutation will not pass to that persons children.

A mutation in sex cell is different.
when the zygote is formed it multiplies to create all the cells in the fetus body - body cells and sex cells.
Again, the mutation can create a wrong enzymes or protein that can cause a malfunction or death, but because the mutation is in all cells we will see the problem in the whole body - and the disease will pass to the children because the sex cells are defected.

A mutation can happen in our life time, in body cells and sex cells.
Exposure to radiation, great heat or great cold, toxins and viruses raise the probability for a mutation.
A mutation doesn't necessarily means a disease - the mutations are the cause of evolution, but most of the mutations are for the worse not for the better.

what helps the body from having the causees of DNA?

how does DNA works?

Athough your answer is thorough and good in ordinary scientific ways, there still is some weirdness to the fact that mutations in sex cells even cause good changes. Seemingly, at least to me, far too few of the changes m would be of actual help, if there weren't any connection between them and something in the other cells, or in the environment, or whatever you may think of (call it God, perhaps). It is thouroughly supressed by most (isn't it?) that random change in sex cells would otherwise have to be totally pathetic as an evolutionary thing, since even fatal changes would be present in next generation, rather than revieled emidiatly. Therefore, this would make sexual reproduction rediculous. Still we prevail. ...