DNA Sequencing: Past, Present, and Future

Over the course of time, the process of DNA sequencing has greatly evolved from something very long, and tedious, and hard, and annoying, to something that is really quick and cool.  We learned about how to do these processes and even did the processes ourself.

Past

This method was first founded by Frederick Sanger in the 1970s.  The whole process of the Sanger method is to locate which tick goes with what letter in groups of three.  From there, we had to use the chart to figure out what DNA sequence the group of three stood for.  In this whole experiment, we examined the sequences of Abby, Bob, and Carol to see if they’re genes are normal or have some sort of disease to them.  Below is pictures of our experiment.

This chart above shows the data we collected from the old data DNA sequencing method.  Let me explain to you what all of this means.  The top most columns show what normal data should look like.  The top being the sequence and the bottom of the two being the protein each set of three translates too.  To determine weather Abby, Bob, or Carol are infected with a disease or not, we had to compare it to the normal DNA sequence.  Each person had to have the same exact DNA sequence as a normal DNA strand.  As you can see (because they are highlighted) not a single person has normal DNA.  Here’s how!

Abby: Abby has what we would call point mutation.  This means that just one point in the DNA sequence is different than regular DNA.

Bob: Here, Bob is effected by what we call truncation mutation.  This means that the gene code is too short.  It stops before gene development is complete.

Carol:  Carol has one of stingiest types of mutation.  The frame shift mutation.  Carol is missing one gene letter.  (In her case it is a T).  This messes up the entire sequence and even creates different proteins than needed.

Present

Today, we solve all of our sequencing problems much simpler: with a laser!

Of course, this was all online.  We followed the steps of the virtual lab to sequence the unknown samples.  Based on the information we received after the procedure, we had to go and figure out what the sample was.  There were six main steps to this lab:

1. Sample prep: First, we had to make sure the DNA was ready to go.  We dissolved the cell in buffer that would eat the cell wall.  Next, the enzymes had to be heated in a bath at 100 degrees Celsius.  The debris is spun in a centrifuge and the contained in a supernatant liquid.  It’s then transferred to the PRC tube.
2. PRC Amplification: From here the steps get intensive.  We added PRC solution to the sample DNA and heat it to copy the DNA stands.  We then load it into the thermocycler to replicate it all.  It does this by constantly separating and doubling the helix of the DNA stands.  It has to be cool here.  And then warm.  This can happen many of times.
3. PRC Purification:  We checked our work using a gel.  Then, we separated DNA from the PRC tube.  Add buffer to separate the DNA and spin the whole PRC solution at 3,000 rpm.  Then discard the tube after removing the collected content.  Then repeat to separate.
4. Sequencing Prep:  As of now, the DNA was purified.  Here, we could get the DNA ready to finally sequence.  There were 12 primers necessary for use, 6 for each strand of the helix.  Multiple primers reduced the possibility of error.  The needed lengths of DNA needed are flagged by the primer.
5. DNA Sequencing:  Here, we had to separate the DNA so it was able to be sequenced.  To do this, you had to use a sequencer that performs gel electrophoresis.  You add a buffer solution to a DNA containing tube.  An electric current is sent through the tube and moves through the solution.  Here is the fun part!  The syringe tube goes through the laser and the laser detects based on color what is what.  Each color represented a letter in the DNA code.  Twelve total tubes are examined.
6. Lastly, we as humans and not computer simulations had to utilize this data and identify the bacteria from this long process we just completed.  The simulation gave you a code which we copied and inserted into blast.NCBI.nlm.nih.gov.  This website included the BLAST feature, or Basic Local Alignment Search Tool.  Pretty much, this tool read the given sequence and compared it to the billions of other DNA sequences recorded.  From here, you could see what bacteria you’re identifying based on the sequence.  In this simulation, we gained the results from 6 samples.  Below are the results:

In real life, this process takes a good chunk of time to complete.  But, it is a lot more quick than scanning row by row an enormous DNA sequence.

Future

Now, we can’t predict what will actually  happen in the future.  Though, the movie Gattaca has a prediction.  It predicts that DNA sequencing will happen instantly and will determine every bit of our lives.  What jobs we have, how long we will live, what schools we get into.  Crazy right!  But, Gattaca is just a movie.  So, until we know for sure, let’s just enjoy the entertainment and the predictions of our lives based on DNA sequencing in the future.