DNA Fingerprinting

We all have individual and unique fingerprints.  These said fingerprints help us to identify a person.  This happens in crime solving and other unique situations, like “Who’s the daddy” shows.  But, did you know that the same thing can happen for DNA.  Yes, you can finger print DNA!  We viewed this in two ways.  First,  was a WEBQUESTTT!  And secondly was like a mini lab thingy magigger.  We will start of with the web quest.

“Part 1.

 

Use your browser to go to NOVA’s web site about “Killer’s Trail,”  the story behind the man who inspired the Fugitive TV series and later the movie version starring Harrison Ford:

http://www.pbs.org/wgbh/nova/sheppard/

 

Click on the “Chronology of a Murder” section and read about the events that led up to the murder trial of Dr. Sam Sheppard.

 

1. In your opinion, what role (if any) did newspaper stories and editorials have in the outcome of the original trial of Dr. Sam Sheppard?

I think that the role of the newspapers and editorials was a large one.  It probably started a large amount of false rumors that could have effected the outcome of the trial based on who read it.

 

Go back to the Killer’s Trail homepage and select ”Create a DNA Fingerprint.”

 

Read about the crime and the suspects then go on to part 2. Answer the following questions about the technique as you go through the simulation:

 

1. What is the function of the restriction enzymes in DNA fingerprinting?

The restriction enzymes cuts the DNA to the pieces that we need.

1. What is the function of  the agarose gel electrophoresis step?

The agarose gel acts like a strainer, it lets smaller parts through but not bigger parts.

1. Why is a nylon membrane used to blot the DNA?

The nylon membrane absorbed the pattern so it was easier to read.

1. What does a dark spot on the X-ray film indicate?

The dark spots indicated the DNA pattern of the saliva.

Part 2.

 

Use your browser to go to Frontline’s “What Jennifer Saw” at

 

http://www.pbs.org/wgbh/pages/frontline/shows/dna/.

 

The material on this site is about a man convicted of rape but later exonerated by DNA evidence. To read a summary of the case, choose the link to Ronald Cotton’s wrongful conviction, then choose “Summary of Cotton’s Case.”

 

In the interviews section, read the interviews with DNA expert Peter Neufeld and lawyer Barry Scheck.

 

Answer the following questions:

 

1. What evidence was initially used to convict Cotton?

A faulty eyewitness identification by Jennifer Thompson wrongly convicted Ronald Cotton.

1. What did the DNA evidence show?

The DNA evidence showed that Cotton’s DNA was not present.

1. How could DNA fingerprinting be used to prevent a false conviction if a case like this was being tried today?

Today, you are able to pick up fingerprints from various parts of the crime.  Using electrophoresis you can match up DNA with the convictee to see if they match up.

1. What percentage of convicts are unjustly convicted of sexual assault cases, according to Neufeld and Scheck?

About 25% of sexual assault cases.

1. The O.J. Simpson trial was one of the most visible trials that attempted to use DNA evidence.  In the end, the DNA evidence was not satisfying to the jury, who acquitted Simpson.  What do Neufeld and Scheck believe about the impact of the O.J. Simpson trial on the use of DNA evidence?

They believed that the main impact of the O.J. Simpson trial is the use of DNA evidence is that it shows how necessary money is in these instances.  The more money you have the easier it is for things to be correct.  You have the money to set correct standards and hire more people to work on the case.  It also highlights the use of bettering technology in our future.”

The second thing we did was use a gel thing to simulate DNA finger printing, like in the part one simulation.  Electrophoresis.  The first step was to ready the cartridges and create the agarose gel.  My group created the gel substance.  We did this by adding agarose and diluted water buffer to one another and stirring it.  From there we had to heat the substance off and on over night so that it was not boiling, but pretty much boiling.  Then, it was just a matter of letting the mixture sit over night and form into a gel substance in the holey containers that other groups made.  The holey containers were contained in a electrophoresis machine where it would chill for a while.

When I say holey containers, I don’t mean legit containers with holes.  I mean more along the lines of like little baby rectangle cut outs in two straight and equal rows of 6.  (You’ll see what I mean in the pictures).

So, what was the purpose of this?  Well, the next step will explain it all.

Once the liquid was formed into the gel, it was time for the main experiment.  We had a bunch of dyes.  These unknown and colorful dyes had a certain charge, which we will worry about later.  These dyes, in a random picking and order, got inserted into the gel holes using an awesome pipet syringe thing.

The final product was all 12 holes being filled with a different dye.  Then came in the electrophoresis part.  This is where the positive and negatives part plays in.  On each side of the machine is one charge.  Red being positive and black being negative.  Once powered and ran over night, we would be able to determine which gel would have which charge by which way the gels moved towards.  If I had kept track of the gels I could give you a data table of where each one went but I didn’t soooo, sorry, lolz.

So, we were able to tell which charge each gel had.  In the real world, you can do this same thing using DNA.  Like we did in the web quest simulation.  Having evolved into what it is today, electrophoresis and fingerprinting has become a great technology that helps us a TON in our everyday lives and crime solving techniques.