The human body consists of approximately 75 trillion cells of 200 varieties. The nucleus of each of these cells holds 46 chromosomes on two strands of DNA. Each strand holds 23 chromosomes, and is one meter long. The DNA is assembled in a double helix shape.
A special packing system allows it to fit in one nucleus of a diameter of 0.006mm. During fertilization, one strand from the egg and one strand from the sperm combine. These two strands of chromosomes contain approximately 60,000 genes.
The genes are the basis for all the processes and structures of life, containing the building instructions of the whole organism and about 3 billion chemical code letters which maintain all the bodily functions and the internal environment. The actual gene does not run the system, it gives a message to the enzymes (proteins) and they run the system. Without a message from the gene there is no activity.
Assuming that one gene is responsible for one enzyme, this would mean the body runs on a minimum of 60,000 enzymes maintaining bodily functions and internal environment. One gene is likely responsible for more than one protein, making it likely that the body relies on over 150,000 proteins. The above is a very basic explanation. For more detailed information please consult an advanced book on cell biology. If you would like to know more about how diseases read the blog post on The Cause of Disease.