Forth Valley College show us how to match human DNA

Forth Valley College lecturer Paul Sweeney talks Falkirk Herald reporter Scott McAngus through the DNA profiling process. Picture: Gary hutchison (133251c)
Forth Valley College lecturer Paul Sweeney talks Falkirk Herald reporter Scott McAngus through the DNA profiling process. Picture: Gary hutchison (133251c)

I’ve always fancied myself as a bit of sleuth, hence my occupation, but I got a chance to see how real ones catch crooks – CSI-style.

TV cop programmes like ‘Starsky and Hutch’, ‘The Equalizer’ or ‘The Professionals’ were particular favourites of mine as a young boy. Starsky was the coolest man on the planet in my eyes, but detective shows have changed a lot since the seventies and eighties.

Science is a major part of murder investigations these days and it’s the “geeks” from the labs who are doing all the cool stuff.

DNA fingerprinting is the most effective scientific process crime agencies have at their disposal and can prove beyond any doubt the guilt, or innocence, of a suspect.

This complicated process was broken down into a fools guide even a simpleton like me could understand by scientist and Forth Valley College tutor Paul Sweeney and I was mesmerised.

Paul (51), from Laurieston has a BSc Honours degree in animal biology and conservation and has taught budding scientists in Falkirk for 14 years. He says popular TV shows are a good thing for science, however “far-fetched” the plots may be.

“We do actually look at the market place and what is happening on television and what people are watching, things like CSI,” he said. “For me as a scientist they are not that interesting, but it does engage the public.

“It is far-fetched. The theory behind some of it is right but there aren’t the computers where you put something in one end and you solve the crime at the other.

“It takes weeks and weeks to do these things, but TV programmes only have an hour or so. But it gets people interested and engaged. Also things like ‘Dara O’Briain’s Science Club are quite good.”

Paul ran me through the stages of determining blood types to match to murder suspects at a crime scene. The first step we did was a Kastle Meyer reagent test using phenolphthaline which is treated to remove all the oxygen.

This is added to the sample of blood followed by hydrogen peroxide (H202), which reacts with the blood and breaks the peroxide down into H2O and leaves an oxygen molecule behind.

The phenolphthaline picks up this O2 molecule and reverts back to its pink colour which will then prove it is blood and be visible for a match. This doesn’t say what type of blood it is, however, so another test is needed.

A and B type blood has proteins while O type doesn’t so if you add A or B antigens to the sample and it doesn’t clot or coagulate then it will be O type. To test for A or B type blood you add A or B antigens and if the blood reacts by coagulating it will tell you the type of blood. It is then tested to see if it reacts positively for another protein called Rhesus. This will tell you if the blood is positive or negative.

The next step is to test the blood DNA which is done through an electrophoresis process. Say you have three suspects and samples from the scene of the crime and a suspect. You would dye each sample of the DNA in small vials and then mix it in a 7000 revs per minute centrifuge for about a minute.

Using a pipette, and very steady hands, we transferred them into tiny wells in a gel. The crime scene sample at the top followed by a space and then the other three in the line of wells.

It’s a delicate process and must be done carefully otherwise the wells will burst. To run the DNA out of the wells into the gel we put it into the electrophoresis chamber then added a saline solution buffer up to the top edge of the gel.

The chamber is then topped up with the buffer solution and a 200-volt electrical current is run through it for about 20 minutes to draw it out into the gel.

The gel is then stained in dye and the DNA samples magically appear. When you have two that look the same you have a match – and your suspect bang to rights.

Science wasn’t my strong point at school. In fact, school wasn’t my strong point. I had too much carry on in my head and like many other people I finally matured enough in my late twenties to settle down and use my brain for something constructive.

The good thing for anyone interested in a career in this field is that Forth Valley College does basic access courses to applied biological sciences right through to degree level opening the industry up to more and more people.

Paul said: “I never really excelled at science at myself. My last report at school, and I won’t say what one it is, said that Paul wouldn’t make anything of himself at sciences. So I was quite late in coming back to science, I was in my early thirties.

“I had a realisation that regardless of what happened at school, science is part of our everyday lives and impacts on almost anything we do. The science process is looking at a problem and coming up with a theory.”

Student Robert Paterson’s story is similar to Paul’s – and my own – in that he went back to education in later life to fulfil his career ambitions.

The 26-year-old from Denny left school at 15 with no standard grades, but is now in the second year of the access course and is hoping to work in the regenerative medicine industry. He said: “Ever since I can remember I’ve wanted to work in a lab. When I was younger I thought I had better things to do with myself than learn, but I got A’s in all my subjects last year which shows you how good the course is.

“The course gives you all the background and lab skills you need to go on to the higher courses which I’ll be doing next year.

“I want to go on and study cell biology at university. I’m really interested in micro-organisms and how they work and how we can use them for a massive variety of things like in regenerative medicine, to try to find cures for things.”