If given the name of a gene
or its ID number, one should be able to find and retrieve its DNA sequence.
Many sequences are given an accession number or a gi number as identification
for database processing. Each and every sequence has its own unique accession
number, but there may be some sequences have more than one accession number.
NCBI’s Entrez Search and Retrieval System is a program that allows search and
retrieval of information from the NCBI database with a variety of search
fields. A good way to narrow down your search is to change the search field in
the Limits section of the program.
Instructions:
1. In
NCBI homepage click Entrez link.
(This
will take you to NCBI’s Entrez Search and Retrieval System.)
2. Select
nucleotide option in the search box.
(This
tells the program which database you wish to search: a nucleotide sequence
search. Or you can click to the database from the hyperlinks above in the black
colored menu.)
3. In search box: type in the name of the gene, an accession number, or a gi number as the search field.
4. Click on the “Go” button.
(The search will be performed.)
5. The
program will provide a list of the search results.
(If
the search was not specific, the list will be very large.)
6. To shorten the list, type in another related
keyword, and click “Go” to perform another search.
7. The program will list all results of the new search.
(Combine the search results by
clicking on the History hyperlink. This will display all previous searches.)
8. To combine the keywords and
display results related to both: Type
in the number that corresponds to the respective keywords and add the Boolean
AND between each.
(Boolean
operators may be used as well:
Intersection
(AND) - only those citations that contain selected terms.
Union (OR)
- citations that contain at least one of the selected terms.
Difference
(NOT) - exclude citations with the selected term.
Note: Boolean operators must be
typed in all capital letters.)
9. Once you have narrowed down your search by combining keywords a few times. You can scroll through and select the result(s) that best describes what you are searching for.
10. To view the information click on the link to your molecule.
11. Once you have found your sequence, Entrez makes it easy to navigate between nucleotide, protein, structure, and MedLine information with hyperlinks to each other.
If you need extra help, try
the Entrez Tutorial Provided by NCBI.
When you are ready, click
here to start.