View source for Biopython/C2/Blast/English


{| style="border-spacing:0;"
! <center>Visual Cue</center>
! <center>Narration</center>

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 1'''

'''Title Slide'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Welcome to this tutorial on''' BLAST''' using Biopython tools.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 2'''

'''Learning Objectives'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this tutorial, we will learn to

* Run '''BLAST''' for the query sequence using Biopython tools.<br/> 

* And parse the '''BLAST''' output for further analysis.



|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 3'''

'''Pre-requisites'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To follow this tutorial you should be familiar with,


* Undergraduate Biochemistry or Bioinformatics<br/> 

* And Basic Python programming 

Refer to the Python tutorials at the given link.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 4'''

'''System Requirement'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To record this tutorial, I am using,

* Ubuntu OS version. 14.10
* Python version 2.7.8
* Ipython interpretor version 2.3.0
* Biopython version 1.64
* And a Working internet connection



|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 5'''

'''About BLAST'''



| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| '''BLAST''' is the acronym for '''Basic Local Alignment Search Tool.''' 


It is an algorithm for comparing sequence information.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 6'''

'''About BLAST'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The program compares nucleotide or protein sequences to sequences in databases 


and calculates the statistical significance of matches.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 7'''

'''About BLAST'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| There are two different ways to run '''BLAST''':

Local '''BLAST''' on your machine.


Run '''BLAST''' over Internet through NCBI servers.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 8'''

'''About BLAST'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Running '''BLAST''' in Biopython has two steps.


First, run '''BLAST''' for your query sequence and get some output. 


Second, parse the '''BLAST''' output for further analysis.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Cursor on Slide Number 8'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We will open the terminal and run '''BLAST''' for a nucleotide sequence.


Open the terminal by pressing ctrl, alt and t keys simultaneously. 

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.

Type, ipython and press enter.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| At the prompt type ipython and press enter.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| At the prompt type:

'''>>> from Bio.Blast import NCBIWWW'''


'''Press enter.'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this tutorial I will demonstrate how to run BLAST over internet using NCBI BLAST service.


Type the following at the prompt:


Import '''NCBIWWW''' module from Bio.Blast package.


Press enter.




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Type,'''


'''>>> result = NCBIWWW.qblast("blastn", "nt", "186429")'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Next to run the BLAST over internet:


Type the following at the prompt,


We will use function '''qblast function '''in the '''NCBIWWW '''module.




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.


Highlight the arguments.


'''>>> result = NCBIWWW.qblast("blastn", "nt", "186429")'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The qblast function takes three arguments:


The first argument is the blast program to use for the search.


Second specifies the databases to search against


The third argument is a your query sequence.




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal. 



| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The input for the query sequence can be in the form of '''GI''' number or a '''FASTA''' file.

Or it can also be a sequence record object.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight the query.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| For this demonstration I am using the GI number for a nucleotide sequence. 


The '''GI''' number is for a nucleotide sequence of insulin. 

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 9'''

'''qblast function.'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The '''qblast''' function also takes a number of other option arguments.


These arguments are analogous to the different parameters you can set on the '''BLAST''' web page.


The '''qblast''' function will return the '''BLAST''' results in '''xml''' format.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Back to the terminal.


We have to use the appropriate Blast program,


depending on whether your query is a nucleotide or protein sequence. 


Since our query is a nucleotide, we will use '''blastn '''program.''' '''


And '''nt''' refers to the nucleotide database.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 10'''


'''NCBI BLAST website'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Details about this are available at the NCBI BLAST webpage. 


http://blast.ncbi.nlm.nih.gov/Blast.cgi




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The blast output is stored in the variable “'''result'''” in the form of an '''xml''' file.

Press enter.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Depending upon the speed of your internet, it may take a few minutes to complete the BLAST search.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Type,'''


'''>>> save_file = open("blast.xml", "w") '''

'''>>> save_file.write(result.read()) '''

'''>>> save_file.close() '''

'''>>> result.close()'''


'''Press enter'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| It is important to save the '''xml''' file on the disk before processing further.


Type the following lines to save the '''xml file. '''


These lines of code will save the search result as '''blast.xml''' in the home folder.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Navigate to your home folder and locate the file.


Click on the file and check the contents of the file.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Open the text file.


'''from Bio.Blast import NCBIWWW '''

'''fasta_string = open("insulin.fasta").read() '''

'''result = NCBIWWW.qblast("blastn", "nt", fasta_string)'''

'''save_file = open("blast.xml", "w") '''

'''save_file.write(result.read()) '''

'''save_file.close() '''

'''result.close()'''

'''result= open("blast.xml")'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Use the code in this text file if you want to use a '''FASTA''' file as a query. 




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Open the text file.


'''from Bio.Blast import NCBIWWW '''

'''from Bio import SeqIO '''

'''record = SeqIO.read("insulin.fasta", format="fasta") '''

'''result = NCBIWWW.qblast("blastn", "nt", record.seq)'''

'''save_file = open("blast.xml", "w") '''

'''save_file.write(result.read()) '''

'''save_file.close() '''

'''result.close()'''

'''result= open("blast.xml")'''



| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here is the code if you want to use sequence record object from a '''FASTA''' file as a query. 




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Type,'''

'''>>>result = open("my_blast.xml")'''


'''press enter.'''



| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Back to the terminal.


The next step is to parse the file to extract data.


First step in parsing is to open the '''xml''' file for input.


Type the following at the prompt:


Press enter.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''>>> from Bio.Blast import NCBIXML'''


'''press enter.'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Next import the module '''NCBIXML''' from Bio.Blast package.


Press enter.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Type,'''


'''>>>records = NCBIXM.parse(result)'''

'''>>>blast_record = records.next()'''

'''press enter'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Type the following lines to parse the Blast output.


A '''BLAST''' record contains all the information you want to extract from the '''BLAST''' output.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us print out some information about all hits in our blast report greater than a particular threshold. 


Type the following 


For a match to be significant, expect score should be less than 0.01.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Type the following code.


'''for alignment in blast_record.alignments: '''

'''for hsp in alignment.hsps: '''

'''if hsp.expect <0.01: '''

'''print('****Alignment****') '''

'''print('sequence:', alignment.title) '''

'''print('length:', alignment.length) '''

'''print('score:', hsp.score) '''

'''print('gaps:', hsp.gaps) '''

'''print('e value:', hsp.expect) '''

'''print(hsp.query[0:90] + '...') '''

'''print(hsp.match[0:90] + '...') '''

'''print(hsp.sbjct[0:90] + '…')'''


'''Press enter key twice.'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| For each '''hsp''' that is high scoring pair, we get the '''title''', '''length''', '''gaps''' and '''expect value'''.


We also print strings containing the '''query''' (query), the aligned database sequence (sbjct) and string specifying the match and mismatch positions (match).


Press enter key twice to get output.




|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight the output.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Observe the output:

For each alignment we have '''length''', '''score''', '''gaps''', '''evalue''' and '''strings'''.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Cursor on the terminal.
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| You can extract the required information using other functions available in '''Bio.Blast''' package.


We have come to the end of this tutorial.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 11'''

'''Summary'''



| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let's summarize,

In this tutorial we have learnt to,


Run '''BLAST''' for the query nucleotide sequence using '''GI''' number.


And parse the '''BLAST''' output file using '''Bio.Blast.Record''' module.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 12'''

Assignment


(use blastp)

result = NCBIWWW.qblast("blastp", "nr", 386828)

non-redundant protein database (nr).
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| For the assignment,


Run''' BLAST''' search for a protein sequence of your choice. 


Save the output file and parse the data contained in the file.


Your completed assignment should have the following lines of code :

As shown in this text file.


Since our query is protein sequence, here we have used '''blastp '''program.


And “'''nr'''” non-redundant protein database for the BLAST search.

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 13'''

'''Acknowledgement '''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The video at the following link summarizes the Spoken Tutorial project. 

Please download and watch it. 

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide Number 14'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The Spoken Tutorial Project Team conducts workshops and gives certificates for those who pass an online test. 

For more details, please write to us. 

|-
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide number 15'''
| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. 

More information on this Mission is available at the link shown. 

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| style="background-color:#ffffff;border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Slide number 15'''
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