OMIM (Online Mendelian Inheritance in Man) is a detailed listing of known human genes that now contains over 10,000 entries. It is a service provided by the National Center for Biotechnology Information, a branch of the National Library of Medicine. When you log onto OMIM, you will begin with a home page that offers a number of alternatives, as well as some background informaiton.
Searching OMIM: In most cases, you will begin by selecting "Search the OMIM Database". This will provide a space in which you can enter the item you wish to search for. If you know the OMIM number for the item you are looking for, you can enter that and check the box below to search only the OMIM number field. If you know the gene designation or the name of the gene, enter that and search by title. If you are only looking for recent changes, you can limit your search to items that have been updated in any time period from the last week to the last year. When you click on "Submit Search", you will be given a menu of items that match your search criteria in some way. These may range from a single item if you are searching for an OMIM number to more than you would expect if your entry does not exactly match anything in the database or if you do not limit the search fields.
Selecting and reading an item: The next step is to select an item by clicking on it. This will cause an extended page of information on the selected item to appear. At the top will be the OMIM number and the preferred names for the item. For example:
*110300 ABO BLOOD GROUP; ABOThis will be followed by several alternative titles that also apply to the same genetic system. Next, there is a table of contents, which provides links to jump to various parts of the extended page (you can also get there by scrolling). In most cases, you will want to start with text, which provides a detailed history of study of the genetic locus in question. For some loci, there is a "Mini-MIM", which provides an abbreviated version of the text providing only a few of the key points. There is also a list of allelic variants that you can go to if you want to examine all of the known alleles at the locus.
Genetic diseases: It is also possible to search OMIM for disease names, including some that you might not think would be genetic. For example, if you enter "scurvy" in the search window and specify title, one entry will appear
240400 HYPOASCORBEMIA.When you click on that entry, you will discover that the human requirement for ascorbic acid (vitamin C) and the nutritional disease scurvy, which is caused by a lack of ascorbic acid, are caused by a defective gene for L-gulonolactone oxidase, which carries out the last step in the synthesis of ascorbic acid in those species that do not have a dietary requirement for ascorbic acid. Thum, OMIM regards scurvy as a genetic disease that can be treated by administering ascorbic acid. From an evolutionary perspective, this is valid, since the human genome does in fact contain the badly mutated remnants of the ancestral L-gulonolactone oxidase gene (sometimes called the L-gulonolactone oxidase pseudogene).
Broad search: If you do not limit your search to "title", additional pages will be found that contain the search term somewhere in the text. For example, a search for "scurvy, not limited to title, will also bring up #309400 MENKE'S SYNDROME. Although this page has nothing directly to do with scurvy, the work scurvy does appear at least once within the extended text. Sometimes this can be useful in finding obscure relationships, but most of the time, it adds extra hits that are better avoided by limiting the search to title.
Gene map: If you select the gene map search, you can either start with a specific gene or a specific chromosomal location and move along the chromosome looking at adjacent genes. Caution must be exercised in interpreting what is presented, however, because exact gene order is still not known in many cases, although it soon should be as data from the human genome project are processed.
Morbid map: Another option is the OMIM morbid map. If you enter a specific genetic disease, such as scurvy, you will enter an alphabetical listing of all genetic diseases that OMIM has catalogued. From your starting point, you can move either up or down the alphabet. This search tends to have a few problems, but generally it works quite well if you know the right terms to search for.
Click here to go to OMIM home page
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