There are many internet sites which fully describe the molecular structure of DNA, its function in the human body, its scientific discovery and its history. Here are a few topics and sites that you may wish to visit:

http://gslc.genetics.utah.edu/
From the University of Utah, a site that explains the basics of genetics, genetic disorders and genetics in society.

http://www.dnaftb.org
An animated primer on the basics of DNA, Genes and Heredity

https://www.nhgri.nih.gov
The website of the National Human Genome Project containing information on DNA, Genes and applications.

http://pbs.org
From PBS you can access many topics on DNA

http://genome.gov/glossary.cfm
From National Human Genome Research Institute, a talking glossary of genetic terms for the non-scientist.