Introduction to OMIM
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us questions, comments or suggestions!
e-mail
us questions, comments or suggestions!
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| TUTORIAL (10-15 minutes) | |
| Online Mendelian Inheritance in Man (OMIM) is a catalog
of human genes and genetic disorders authored and edited by Dr. Victor
A. McKusick and his colleagues at Johns Hopkins and elsewhere, and developed
for the World Wide Web by NCBI, the National Center for Biotechnology Information.
The database contains text information on human genetic conditions, disorders
and diseases, with references to the biomedical literature. It also contains
copious links to MEDLINE and sequence records in the Entrez system, and
links to additional related resources at NCBI and elsewhere.
Searches are done by entering one or more terms in the search text box. The search will return a list of accession numbers which link to records matching the query terms. |
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OMIM can most easily be accessed from the NCBI Home page at www.ncbi.nlm.nih.gov. At the top of the page is a navigation bar, as shown in the image to the left. Click on the "OMIM" link (circled in red) to go to the OMIM home page |
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The top of the OMIM home page is shown in the
graphic to the left. Again, there is a navigation bar at the top with a
search box immediately below it. Type "Sickle Cell Anemia" into the search
box, then click on "Go". The Entrez search engine will return a list of
OMIM records corresponding to the search terms.
The search terms are ranked by statistical relevance to the query. The two accession numbers in red correspond to records which describe the symptoms of the disease (#603903), and information about the protein which causes the disease, the b chain of hemoglobin (+141900). |
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Click on the link "#60903". A screen that looks
like the image to the left should appear. This screen provides an in-depth
summary of the Clinical features, Diagnosis, Gene Therapy, Molecular Genetics,
Population Genetics, etc. of Sickle Cell Anemia.
This screen is rather technical because it is intended for physicians and researchers. Therefore a somewhat more accessible explanation of the Sickle Cell Phenotype is provided. |
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Erythrocytes are virtually empty, except that
they are packed with Hemoglobin, an oxygen-binding protein. Hemoglobin
(HBB) is a tetrameric protein composed of 2
b
globin chains and 2 a
globin chains. b
globin is a peptide chain which contains 147 amino acids. It folds
in such a way as to bind a porphyrin ring with an iron atom.
Click on the link "+141900". A screen that looks like the image to the left should appear. In the left box find "Allelic Variants" and click on the "View List" link. Now scroll down the list until you find "0243 HEMOGLOBIN S [HBB, GLU6VAL]". Click on the link. In this variant of b globin, the 6th amino acid is valine instead of glutamic acid. This screen provides an in-depth summary of the molecular structure and function of the S variant of b globin (HBB), as well as the many other variants. The screen is rather technical because it is intended for physicians and researchers. Therefore a somewhat more accessible explanation of the Sickle b Globin is provided. |
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NOTE:
There is a common misperception that for every gene there are only 2 alleles.
For example eye color is supposedly determined by one gene (THIS
IS WRONG!) which has 2
alleles ... "B" for brown eyes and "b" for blue eyes (THIS
ALSO IS WRONG!).
In fact, OMIM shows us that, as of Jan. 28, 2006, there are at least 535 different alleles of the HBB gene! |
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| EXERCISE
(10 minutes)
Use OMIM to answer the following questions. Turn in the answers to the Instructor.
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Back to "INDEX
for ENTREZ and Data Base Searches"
RETURN TO SITE MAP |
