http://www.ncbi.nlm.nih.gov/disease/index.html
Genes and disease Cancer uncontrolled cell_division Immune_system fighting invaders Metabolism food and energy Muscle and bone movement and growth Nervous_system mind and body Signals cellular messages Transporters pumps and channels THE QUEST_FOR an understanding of how genetic factors contribute to human disease is_speed gathering. Most notably, the draft sequence of the human genome is now available. This rough sketch provides us with the first holistic view of our genetic heritage and is a significant landmark on_the_road to a complete human genome reference sequence. This will_be a fundamental resource in future biomedical research. The 46 human chromosomes (22 pairs of autosomal chromosomes and 2 sex_chromosomes) between them house almost 3 billion base pairs of DNA that contains about 30,000-40,000 protein-coding genes. This_is a much smaller number than predicted-only twice as_many as in the worm or fly model organisms. The coding regions make_up less_than 5%of the genome (the function of the remaining DNA is not clear) and some chromosomes have a higher density of genes than others. A_great_deal of effort over the past ten years has_been put_into creating a physical map of the human genome-ordering genes within the genome by placing landmarks to navigate by. This physical map has_provided an excellent framework for completing the draft sequence as_well_as assisting directly in the identification of about 100 disease genes. MOST OF THE genetic_disorders featured on this web_site are the direct result of a mutation in one gene. However, one of the most difficult problems ahead is to find_out how genes contribute to diseases that have a complex pattern of inheritance, such_as in the cases of diabetes, asthma, cancer and mental_illness. In all these cases, no_one gene has the yes/no power to say whether a person has a disease or not. It is likely that more_than one mutation is_required before the disease is manifest, and a number of genes may each make a subtle contribution to a person's susceptibility to a disease; genes may also affect how a person reacts to environmental factors. Unraveling these networks of events will undoubtedly be a challenge for_some_time to come, and will_be_assisted amply by the availability of the draft (and complete) sequence of the human genome. We welcome feedback in the form of suggestions and comments. Please send mail to: info@ncbi. nlm. nih. gov Tel:(301) 435-4920 National Center for Biotechnology Information National Library of Medicine National_institutes_of_health Building 38a Bethesda MD 20894 USA