1.
Online
Mendelian
Inheritance in
Man (OMIM)

2.
INTRODUCTION:
• Online Mendelian Inheritance in Man (OMIM) is a continuously updated catalog of
human genes and genetic disorders and traits, with a particular focus on the gene-
phenotype relationship. As of 28 June 2019, approximately 9,000 of the over 25,000
entries in OMIM represented phenotypes; the rest represented genes, many of
which were related to known phenotypes.
• This database was initiated in the early 1960s by Dr. Victor A. McKusick as a catalog
of mendelian traits and disorders, entitled Mendelian Inheritance in Man (MIM).
• The online version, OMIM, was created in 1985 by a collaboration between the
National Library of Medicine and the William H. Welch Medical Library at Johns
Hopkins. It was made generally available on the internet starting in 1987.
• In 1995, OMIM was developed for the World Wide Web by NCBI, the National Center
for Biotechnology Information.

3.
OMIM classification system:
Each OMIM entry is given a unique six-digit identifier as summarized below:
• 100000–299999: Autosomal loci or phenotypes (entries created before May 15, 1994)
• 300000–399999: X-linked loci or phenotypes
• 400000–499999: Y-linked loci or phenotypes
• 500000–599999: Mitochondrial loci or phenotypes
• 600000 and above: Autosomal loci or phenotypes (entries created after May 15, 1994)
In cases of allelic heterogeneity, the MIM number of the entry is followed by a decimal point
and a unique 4-digit number specifying the variant. For example, allelic variants in the HBB
gene (141900) are numbered 141900.0001 through 141900.0538.
Because OMIM has responsibility for the classification and naming of genetic disorders, these
numbers are stable identifiers of the disorders.

4.
Symbols preceding MIM numbers:
Symbols preceding MIM numbers indicate the entry category:
• An asterisk (*) before an entry number indicates a gene.
• A number symbol (#) before an entry number indicates that it is a descriptive entry, usually of a
phenotype, and does not represent a unique locus. The reason for the use of the number symbol is given in
the first paragraph of the entry. Discussion of any gene(s) related to the phenotype resides in another entry
(or entries) as described in the first paragraph.
• A plus sign (+) before an entry number indicates that the entry contains the description of a gene of known
sequence and a phenotype.
• A percent sign (%) before an entry number indicates that the entry describes a confirmed Mendelian
phenotype or phenotypic locus for which the underlying molecular basis is not known.
• No symbol before an entry number generally indicates a description of a phenotype for which the
Mendelian basis, although suspected, has not been clearly established or that the separateness of this
phenotype from that in another entry is unclear.
• A caret (^) before an entry number means the entry no longer exists because it was removed from the
database or moved to another entry as indicated.

5.
Basic Search
For basic searches, simply enter the terms in the search box and click the
'Search' button:
• duchenne muscular dystrophy
• The search engine will search for them in any order, ranking the entries
containing all the terms higher than entries containing some of the terms.
• Searches are case-insensitive, so a search for 'duchenne', 'Duchenne', or
'DUCHENNE' will return the same entries.

6.
Boolean Operators
Like most search engines, the 'AND', 'OR' and 'NOT' boolean operators are supported. For
example:
• duchenne AND muscular AND dystrophy
which could also be written as:
• +duchenne +muscular +dystrophy
Or this search:
• muscular AND dystrophy NOT duchenne
which could also be written as:
• +muscular +dystrophy -duchenne
Note that boolean operators must be in UPPER case and it is a good idea to use parentheses
to set operator precedence.
• (duchenne AND dystrophy) OR (becker AND dystrophy)

7.
OMIM
Gene Map
and Morbid
Map
The OMIM Gene Map and Morbid Map present
the cytogenetic locations of genes and disorders,
respectively, that are described in OMIM. Only
OMIM entries for which a cytogenetic location
has been published in the cited references are
represented in the Gene Map and Morbid Map.
The OMIM Gene Map can be searched by gene
symbol (e.g., "SOD1"), chromosomal location
(e.g., "5", "1pter", "Xq" ), or by disorder keyword
(e.g., "Alzheimer").

8.
LIMITATIONS:
OMIM does not have a complete list of all genetic disorders
contained in it; these have to be searched by name or symbol.
It also does not provide facilities for the clinical evaluation and
genetic testing of patients of suspected genetic diseases.
For these types of queries and information, other sources such
as Genetic Alliance, NORD (National Organization for Rare Disease)
and Gene Tests may be useful.