So welcome to MOOC-NPTEL course on Bioengineering, an Interface with Biology and Medicine.
In the last few lectures, I tried to give you some of the problem statements, some bigger
problems towards which all of us have to work together whether we are biologist or engineers.
Actually, you know, we have to think about the goal of how to solve those major problems.
I also try to provide you an interface with clinicians to give you some motivation that
in which way engineering discipline can help medical scientist and clinicians for our day
to day medical problems.
To understand in which way the medical field can also benefit from the engineering tools
and various insights you can bring in now from the engineering point of view.
In this slide I thought it might be good idea to introduce you to some of the bioinformatics
tools.
Some time even if you do not have an opportunity to work in a vet laboratory to do the experiments
yourself, you can actually obtain lot of data which is publically available now a days in
different databases and repositories.
And then if you know some of the open access software and tools, you can then try to download
the data available already and then make use of the data and then try to understand in
which way people are studying genes and proteins.
So that is something which you can do from your own system, your own computers by sitting
at your own room.
You need not to work in a laboratory setup.
So even before we dig deeper into the fundamental concepts, I thought it is good idea to begin
with some of the bioinformatic assignment.
To do this, I will take help of one of my teaching assistants.
We will first try to understand and explain, you know, more information how you can retrieve
for a given gene.
So in my previous lectures I had talked to you about, you know, how people target specifically
a given gene, look at their sequences and how you can use technologies like polymerase
chain reaction to amplify the genes.
So first of all you know how to get a gene sequence.
Again you need to use the bioinformatics tools.
You can go to NCBI portal where you enter the gene name or accession ID.
And then you will see how much information is already available for that given gene.
Then in the tutorial sections you will see in a stepwise manner how this assignment could
be performed.
So I will hand it over now to my TA and after doing the assignment, we will also give you
some problem statements and some assignments which you can do at your own place.
I am Apoorva Venkatesh.
I am a final year PhD student under professor Sanjeeva Srivastava and I am your TA for this
course.
This bioinformatics assignment will teach you how to study genes using NCBI and their
evolutionary relationships.
NCBI provides a variety of databases and computational tools which are freely accessible for use
by the research community.
NCBI is also home to PubMed which many of you may have used for literature searches.
In today's assignment, we will learn how to retrieve the sequence of a gene?
How to identify similar sequences and how to compare multiple sequences to study their
evolutionary relationships.
Let us begin with the first question.
You have been given an accession number 3040 which is a unique identifier given to a DNA
or protein sequence.
We need to fill this table by getting all the information about this gene.
So let us get started.
It would be great if you could do this along with me on your computers.
Type NCBI into your Google browser.
So this brings us to the NCBI website.
We will not be able to explore all the features of NCBI today.
However, I would highly recommend that you go through some of these resources after this
tutorial.
You can begin with the how to link, that is up here.
This will teach you how to accomplish specific tasks at NCBI.
Now I am going to click this link and this will give us a list of how tools.
For example, you may want to know how to retrieve all sequences for an organism or taxon.
You may want to know how to find the function of a gene or gene product.
View all SNPs associated with a gene.
Or you may want to know how to obtain the full text of an article.
So on the left is a list of resources the NCBI provides.
You may want to use some of them depending on your objectives.
So now let us get back to our assignment.
The first thing we will have to do is to type the accession number in the box here and click
gene from the dropdown menu.
Now we say search.
So this page will give us all the details we are looking for.
Please fill the table as you move along.
Our first task is to find out the gene name.
So this gene encodes a subunit of the protein hemoglobin.
I am sure you have heard of this protein earlier.
Hemoglobin is a protein molecule in red blood cells that carries oxygen from the lungs to
body tissues.
Here you can see that this page was last updated on 24 December, 2017.
The official gene symbol is HBA2.
But however, you will also see from this list that not everyone uses this official symbol
in their publications.
This can also be called HBH, HBA-T2, etc.
Gene type is a protein coding gene and this summary here gives us information about the
gene and its functions.
Now if you scroll down further, you see genomic context.
So genomic context describes where the gene resides.
So this gene resides on chromosome 16 in the p arm at 13.3 region.
Now if you scroll down further, this section here shows us the direction in which the gene
is read.
So this particular gene HBA2 is read towards the right.
Now we scroll down further and we go and click on HBA2 to get us more details about this
gene.
So this will give us the length which is 864 base pairs.
So if you click on this gene, you will get all the information on the gene.
And if you further click on this green section, you will get information on the messenger
RNA as well as in the translated protein.
So now let us zoom into 1 particular section of this gene
and click zoom.
Now if you zoom into 1 of the locations, you will be able to see the variations associated
with this gene, darker the colour, more deadly the variation.
So notice this particular variation.
As you will notice, this is in a very dark colour.
This indicates a very deadly variation and if you zoom into this particular section,
you will notice that this also has a PubMed citation.
So now let us scroll upwards.
You will see that this gene belongs to homo sapiens, obviously because this is human hemoglobin
subunit alpha 2 gene.
This particular organism belongs to the superkingdom Eukaryota.
To know more about this organism, we can go and click on to this link.
And we can click on to genome to get more information about the genome of this organism.
Now as you know that this particular gene belongs to chromosome 16.
So we go to chromosome 16 and you will see that the size of this chromosome is 90.34
megabases and it in codes 1920 genes.
So with this information, you will be able to complete this table.
Now let us go back to our assignment.
What we have is a Gene ID 3040.
NCBI had thus fill in all these details.
The official full name, hemoglobin subunit alpha 2.
Date of last update 24 December, 2017.
The gene symbol is HBA2.
It is a protein coding gene.
The location is on chromosome 16 in the p arm at region 13.3.
The size of the gene is 864 bases.
The organism is Homo sapiens.
In the superkingdom, Eukaryota.
The size of the chromosome 16 is 90.34 megabases which encodes 1920 genes.
So this brings us to the end of the first part of this assignment.
The next assignment is a very small one.
You have been asked to enter the FASTA sequence of this gene in the box below.
So let us go to NCBI website again.
Let us type 3040 in the search box.
We type gene and press search.
So this brings us to the same page.
If you scroll down, you will be able to see FASTA here.
If you click on FASTA, you will get this particular nucleotide sequence for this gene.
Let us copy this sequence and enter it in the box.
So this brings us to the end of assignment 1B.
Alright, so you are now familiar with looking at genes and sequences and what all information
one could obtain just by doing simple bioinformatic analysis, right.
So now let us go one step further.
Let us study how to compare sequences of one particular gene between different organisms
and to see how simpler or different they are.
Similarly we will also compare the protein sequences and I am sure, you will understand
that the proteins are much more complex than DNA.
And by comparing protein sequences across different organisms, one could actually find
out lot of information which is biologically relevant and it may sometime gives us the
clues for even process like evolution how it has happened.
Such sequence similarity searches can actually also help us to do to study evolutionary relationship.
Or it can allow us to identify the proteins with similar functions.
So this type of analysis which you can do using bioinformatics tools, is known as multiple
sequence alignment and it can be best performed using various open access tools including
the Clustal W or Clustal omega which we are going to demonstrate you in the tutorial section.
Before we move on to the next assignment, I would like to talk to you about a very popular
feature of NCBI known as BLAST.
BLAST stands for basic local alignment search tool.
It allows you to take an input sequence and compare it to a database to see if anything
similar has already been found.
It can be very useful for studying unknown sequences or if you want to see how similar
your sequence is to other sequences.
The most commonly used feature is nucleotide BLAST.
So let us click on NBLAST which is Nucleotide BLAST.
This will take us to the BLAST page where you will see that we need to enter a query
sequence which is nothing but our input sequence which we need to search against a database.
Let us take the FASTA sequence of the hemoglobin alpha chain that we just pasted.
You can choose a human database if you know your protein is a human protein or a mouse
database or if you want to see results from other species, you can choose other.
We will click on other.
This dropdown menu here gives us a list of many databases.
We will select nucleotide collection which is a combination of all nucleotide databases.
Now let us click BLAST.
Here you will see a whole bunch of red lines which BLAST has found.
These represent sequences similar to our input sequence.
Top one here, is our query sequence which goes from 1 to 864 base pair.
The colours here tell us how closely the results match our query or input sequence and the
length of these bars tells us how much they line up with our query.
So you will see there are some which line up perfectly, where some do not.
When you scroll down, you will get a list of sequences producing significant alignments.
You have a maximum score, a total score and a query cover which is the percentage match
with the query and an E value which is the measure of how likely something can occur
by chance.
Lower the E value, better the result.
You will notice that the first few matches have 100% query cover which means that they
are 100% identical.
While you will also see that as you go lower, down this table, you will find matches with
different species.
The alignment section which is further below here, gives you the actual nucleotide sequences
and matches for each of the results.
For example in the first case, there is a 100% match; therefore, no gaps.
So now let us get back to our assignment.
You have been given a protein accession ID which is NP 000508.1.
You have to get details for this protein using NCBI.
We have done this before for a gene.
We will now does the same for this particular protein.
Let us type the accession ID in the search box.
So let us type the accession ID in the search box and now we will select protein from this
dropdown menu and click search.
So here you will see a very similar to what we saw for the gene.
You can actually get all the details for this particular protein.
So the protein name is hemoglobin subunit alpha.
The organism name is Homo sapiens.
The sequence length is 142 amino acids.
The locus is NP 000508.
And now when we run a BLAST search, so now let us run a BLAST search and select PDB here.
The accession number is given in this particular query box and we click on BLAST.
So this particular page will give you details about the BLAST search as you see here, very
similar to what we saw earlier.
Just as you saw earlier, there are 106 BLAST hits on 100 subject sequences and you will
find similar bars here which represent similar sequences.
And if you scroll down further, you will see that the first hit is identical to your query
sequence and you will take the PubMed ID from here which is your PubMed accession ID.
So now let us go back to our assignment and fill the table.
The details for this protein are the protein name is hemoglobin subunit alpha.
The organism name is Homo sapiens.
Sequence length is 142 amino acids.
The locus is NP 000508.
The number of BLAST hits 106 and the PDB ID.
In the fourth part of the tutorial, you have been given a
list of accession IDs.
You have to find out how the sequences are evolutionarily related.
For this, we will type all the accession IDs in the search box on NCBI home page.
Now we will choose protein from the dropdown menu and we will click search.
We will now be able to see all 5 proteins on a single page.
So we do not have to go to each protein individually to take the FASTA sequence.
Simply click on summary and click on FASTA.
Or we can also go to FASTA text so that we get all sequences on 1 page.
So let us copy them, go to Google browser and type Clustal Omega.
Clustal Omega is a multiple sequence alignment program.
It allows us to perform multiple sequence alignments of divergence sequences.
Evolutionary relationships can be seen via cladograms or phylograms.
Copy the FASTA files into the box here.
Keeping all other default parameters constant, click submit.
So as you see the sequences of all the 5 proteins are lined up against each other.
If you select show colours, you can visualize variations and gaps in the sequences.
Now click on the phylogenetic tree to get an idea about the evolutionary relationships.
What you see here is the cladogram.
This is a neighbour joining tree without distance corrections.
Now let us copy this into our document.
So let us paste the cladogram in this document.
You will see here that A and B are closely related while B is somewhat related to A and
B, while C and E are distantly related from all.
So this is how you will get an idea about evolutionary relationships.
This brings us to the end of the bioinformatics assignment 1.
Hope this was very useful.
Thank you.
Alright so in conclusions I am sure you are now convinced that just by doing bioinformatic
analysis using some open access tools, you can get lot of understanding of biologically
relevant information.
In this assignment, we slowly built your, you know, confidence, you try to do some information
for looking at the gene, its sequences, its sequence homology and its different similarity
with that sequences.
We then try to explain you how computational tools could be used to study the evolutionary
relationship just based on the protein sequences.
In another lecture in the coming week, we will also try to study how to visualize protein
structures and protein-protein interactions using some of the bioinformatic tools.
We will also study the pathway analysis and we will learn how to perform molecular assimilation
and docking experiments to study the protein drug interactions.
Thank you and see you next week.