Bioinformatics Lab01.docx

LAB 1 EXPLORING NCBI
[Software needed: web access]
The National Center for Biotechnology Information (NCBI) maintained by the US National
Library of Medicine and National Institutes of Health is one of the world’s most important
resources and repositories for biological data. This fantastic online resource provides an
extensive network of databases cataloging an ever-growing wealth of genetic, medical, and
biochemical information from all walks and crawls of life. Entire genomes, from viruses to
humans, are compiled, organized, and cross-referenced within these networks, such that surfing
the genome can be almost as easy as surfing the web.
But you have to know a) what you’re looking for, and b) what you’re looking at to get anything
out of these databases. This is what this first lab is going to help you do. Note that Google and
other search engines typically do not index database-driven websites, which is why it cannot be
used for searching for information that is stored at NCBI (nor does it handle sequence searching
well, especially in the case of protein sequences).
The primary portal for accessing data at NCBI is called Search NCBI. But first, let’s start by
visiting NCBI’s website and examining the interface, which undergoes constant change.
1. Open your Web browser and go to NCBI’s homepage: www.ncbi.nlm.nih.gov. This page
provides links to all of NCBI databases and resources. It’s worth exploring here just to
get a better idea of the scope of NCBI. If you click About the NCBI you will be taken to
a page summarizing some of these resources. You can also check out the NCBI
Handbook (http://www.ncbi.nlm.nih.gov/books/NBK21101/) for more information.
Figure 1. The NCBI homepage.

2. Now let’s move to the Search NCBI (formerly known as GQuery or Entrez) portal – select
All Databases from the navigation bar at the top of the NCBI start page and click “Search”
beside the empty field. First, scan down the assortment of databases queried through this
portal. You will notice there is everything from the biomedical literature at PubMed to
nucleotide databases, taxonomy databases, protein structure databases, and expression profile
databases. Let’s see what happens when you do an unguided search on the site. In the
"Search NCBI" box, type in bacteria. The output is a summary page of the number of hits in
each section. A search of bacteria gives millions of hits – not very helpful. We need
specifics.
Figure 2. The Search NCBI portal page with bacteria used as a search word.
3. Usually when searching these databases, you have either a region of DNA or a protein (or
protein function) of interest. For this lab you’ll be using a gene from Arabidopsis
thaliana, a small flowering plant that is like the fruit fly of the plant world as it has a
comparatively rapid life cycle and requires little space to grow. The protein product of
this gene is recorded under accession number NP_001318308, and it is an E3 ligase,
involved in ubiquitination of proteins, which is a signal for their degradation.

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Box 1. Accession Numbers and Version Numbers (and GI Numbers…)
An Accession number is a unique identifier for a particular sequence record. An accession
number is assigned to a specific record and stays with that record forever. In other words,
Accession numbers track a particular record and do not change even if the information in the
record is changed at the author's request (e.g. if a better annotation or more complete sequence
is provided). Accession numbers are usually a combination of a letter(s) and numbers, such as a
single letter followed by five digits (e.g., U12345) or two letters followed by six digits (e.g.,
AF123456).
Version numbers follow the Accession number and indicate the revision history of that entry
starting with 1 and increasing with each revision. The standard format is Accession.Version.
A GI number (GenInfo Identifier – sometimes written in lower case, "gi") was simply a series
4. Go back to the Search NCBI portal page and try a more focused search. Use the search terms
found associated with the gene sequence we’ll be using with the GenBank Field Qualifiers
shown below (a full list of qualifiers is presented in Appendix 1). Try the four different
searches presented below and look at the number records, specifically “Protein” records,
found:
 gene keywords
e.g. ubiquitin-protein ligase
 gene keyword AND organism
e.g. ubiquitin-protein ligase AND Arabidopsis thaliana
 gene keyword [PROT] AND organism [ORGN]
e.g. ubiquitin-protein ligase [PROT] AND Arabidopsis thaliana [ORGN]
 accession or GI number
e.g. NP_001318308
That narrowed things down significantly!
Note that using parentheses can be very helpful in making sure you get exactly what you
want. For example:
SMC AND (yeast [ORGN] OR Arabidopsis [ORGN])
is a very different search than
SMC AND yeast [ORGN] OR Arabidopsis [ORGN]
Also, using quotation marks can also dramatically affect your search (ie: 16s rRNA vs. “16s
rRNA”).
Finally, always capitalize the Boolean operators such as AND / OR / NOT.
Ultimately, the most specific search items you can use are accession numbers.

Box 2. NCBI Help
This is a good time to get familiar with NCBI’s thorough Help index for future reference. With
this index, you should be able to access most of the background you need for understanding
how these databases work on your own (there’s also an NCBI YouTube channel if you’d like to
check that out too).
1. At the bottom left of the NCBI homepage find the “NCBI Help Manual” link.
Click on it. Then access the “Entrez Help” section.
2. You are now in Entrez Help. The Entrez collection of databases is queried when you use
the Search NCBI interface. Note the contents that explain everything from search options
to saving sets of records.
3. Notice that under the section Entrez Searching Options some other appropriate
qualifiers are given, as illustrated on the previous page.
5. Search for our accession number of interest (e.g. NP_001318308 from above) through the
Search NCBI portal page. It should give you 1 protein sequence hit. Click on it (it is a
hyperlink) so that you get its full GenBank description (you can also click on the
“armadillo/beta-catenin repeat protein [Arabidopsis thaliana]” link at the top of the page
as the NCBI system recognizes that you’ve entered a protein identifier and hence
provides some summary information for that above the numerical overview of results).
of digits that was, until recently, assigned consecutively to each sequence record processed by
NCBI. The GI system of identifiers ran in parallel to the Accession.Version system; therefore, if
the DNA or protein sequence changed in any way, it would receive a new GI number.
Example: When a new entry was submitted to GenBank it was assigned an accession number
(say AF000001). Since this is the first version the Accession would be appended with ‘.1’, so it
would look like AF000001.1. At the same time was given a GI number (say GI:1234567). Now
imagine that the researcher who originally submitted the record wanted to update the
information. The updated record would keep the same Accession number, but would increase in
version number (AF000001.2). The new record would have been given a completely new GI
number (say GI:9876543).
Why is this important? The Accession number will always give you the most up-to-date
information on a record, while the Accession.Version will always take you to a specific record.
There are times when you want the most current information, and other times when you want to
point to a particular piece of information from a particular point in time (e.g. a particular record
that you did an analysis with), even if more information has been subsequently added. Note that
as of September 2016, NCBI started phasing out the use of GI numbers. The use of
Accession.Version form is now recommended for accessing a particular record, instead of the
GI number. GI numbers are not to be confused with Entrez Gene IDs, which are another
referencing system that NCBI uses entirely!

Figure 3. GenBank record for accession NP_001318308, in GenPept format.

6. Notice all the hyperlinks within the text. It looks messy but is in fact straightforward. For
example, for taxonomic information, click on the SOURCE ORGANISM hyperlink. Some
records have links to the primary publication where this sequence was originally cited in a
PUBMED number hyperlink (not the case in the above example, but there is a PubMed
reference for the sequence). Click around on different links and see what you find.
a. What is the taxonomic lineage of your organism?
b. Has the genome of this organism been sequenced, i.e. is there a Genome Project?
c. If so, can you find the accession for the full sequence or one of the chromosomes?
 To find out much more information on the structure of the GenBank file at
http://www.ncbi.nlm.nih.gov/Sitemap/samplerecord.html
7. Go back to the GenBank record and click on the CDS link, just above the actual sequence
(circled in red in Figure 3 on the previous page).
a. Where did this take you or what happened when you did this?
8. Go back to the GenBank record and examine the Related Information section on the lower
right. This gives you direct links to other databases with information on this query. Find the
Gene link.
Figure 4. The Related Information menu for NP_001318308, to the right of the record. The
arrow is pointing to the “Gene” link.
9. Select Gene from the Related Information menu. This is a great starter resource at NCBI.
Scroll through the different sections. Use them to answer the following questions.
a. Where is your gene’s location in the genome? (Tip: hover with your cursor over the
green bars in the “Genomic regions, transcripts, and products” section; the green
bars represent the gene in the sequence viewer)
b. How many exons do you see in this gene? Tip: how many green boxes are there?
c. What are the names of the genes surrounding it (i.e. what is its “Genomic context”)?
d. Does it have any conserved domains? What are they called? (Tip: use the “Related
Information” link to Conserved Domains on the right of the Gene page)

e. After exploring conserved domains go back to the Gene page. What biological
process (Gene Ontology terms) is this gene involved with (scroll down!)?
Figure 5. GenBank Gene page for At2g28830 (also known as PUB12), the gene that encodes
NP_001318308.
10. On the Gene page, there are also Additional links to examine a gene’s structure, function
and phylogenetic relationships further. The navigation sidebar on the right has an
“Additional links” hyperlink which will take you to the bottom of the page, where they’re
found for most genes. Click [+] Gene LinkOut to see them.
a. Click on Additional Links. What kind of information is in this section?

 Click around and explore the variety of ways that data for PUB12 are interconnected and
displayed (don’t worry, you can’t break anything). Using the Related Information links
can you find any publications associated with this gene? What about gene expression
data? The next page shows the related “RefSeq RNA” record for the corresponding
encoding mRNA (NCBI’s RefSeq aims to provide canonical “reference” sequences –
genomic, mRNA, CDS, protein etc. – for many model organisms).
b.Why is the length of the mRNA different from the value you can calculate from the start
and stop positions in Question 9a?
Figure 6. RefSeq RNA linked from Gene page for At2g28830

Box 3. Helpful Hints for NCBI searches
On most NCBI search pages (except, oddly, Search NCBI) click on “Save Search” or “Create
Alert” below the search box. Register for an account and save your search. You can also
combine previous searches using the History tab and the search numbers listed within it, as
well as save your searches by registering for a My NCBI account, so you don’t have to keep
redoing the same searches in the future.

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