she electronically signed in to the building.
‘Some experiments need constant monitoring,’ she said, ‘so the labs are always open. Some of the staff almost live here at times.’
‘My, my,’ Geoffrey said, seeing Marina in the light. ‘That’s quite a face. Is this a police job, Sid?’
‘No,’ both Marina and I said together.
‘Walked into a door, did you?’ Geoffrey said sarcastically. ‘Correction. Two doors. Very careless.’
We went up in the lift with Geoffrey tut-tutting under his breath.
We walked down endless corridors with cream walls and blue vinyl flooring. Half of the corridor floor space was taken up with rows of grey filing cabinets interspersed by three-foot high cylinders with yellow triangular warning labels stuck on them: ‘Liquid nitrogen — Danger of asphyxiation’. Marina punched numbers into another electronic lock that agreed with a beep to give us entry to her domain.
She flicked on the stark overhead fluorescent lamps and went to sit at one of the laboratory benches where she carefully removed the plastic bag from her pocket and put it in a fridge.
‘That will keep it fresh for a while,’ she said. ‘OK, Doc, do your worst.’
Geoffrey worked for nearly half an hour, cleaning and tidying up the wounds, injecting some local anaesthetic, and finally closing the gaps with two rows of minute blue stitches. I had brought my camera up from the car and, much to Marina’s annoyance, I took a series of shots as her wounds were transformed from an ugly bleeding mess to two neat lines, one horizontal in her eyebrow and the other vertical through her lower lip. With a rapidly blackening eye, she looked like one of those advertisements for wearing seat belts.
‘There,’ he said at last. ‘I’ll have to take them out again in about five or six days but you won’t be able to spot the scars in a few weeks.’
‘I thought stitches dissolved these days,’ Marina said.
‘Those are mostly used for internal stitching,’ he replied, ‘and staples are ugly and tend to leave scars. Nothing like good old-fashioned catgut stitches if you want to leave no trace, or this blue nylon as we tend to use these days And don’t tie them too tight or they pull. These should be fine.’
‘Thank you,’ said Marina. ‘Can I get back to work now?’
‘Sure,’ said the doctor, ‘but those might be a bit sore when the anaesthetic wears off. And I should give you a tetanus shot, unless you’ve had one within the last ten years.’
‘I have no idea,’ said Marina.
‘Well, you’d better have one just to be sure. I brought some with me.’
He stuck a pre-loaded hypodermic needle into Marina’s bottom as she bent over a lab bench.
‘What do you do here?’ he asked. ‘Reminds me of medical school.’
‘This is a haematology lab,’ she said. ‘We look at blood to try and find a marker for various types of cancer. We take blood cells and cut the proteins into amino-acid chains using the enzyme trypsin. Trypsin is, of course, a protein itself.’
Of course, I thought.
‘We look at the chains of amino acids which make up the proteins and see if there are markers which are certain cancer specific. We pass the chains through this mass spectrometer,’ she pointed at a long grey cabinet that reminded me of a deep freeze. ‘It determines the relative masses of each chain and if there is a variation we are not expecting this may be the marker we are looking for.’
I was completely lost but Geoffrey seemed to understand and he was nodding furiously as he moved around, inspecting the mass spectrometer from every angle.
‘Glad to see my taxes are going to a good home,’ he said.
‘No, no!’ said Marina. ‘This institution and all the research we do here is funded by charitable contributions from the public to Cancer Research UK. We are not supported by taxation. It’s very important to us that people know that.’
‘Sorry,’ said Geoffrey. ‘I stand corrected.’
Marina nodded and took the plastic bag out of the fridge.
‘Now from this little lot,’ she said, getting back to her ‘in lab’ mode, ‘what I want is a DNA profile. DNA is the code for making cells. Proteins are the bricks from which the cells are built. The DNA strands are the architect’s plans that show how the bricks go together to build the cell structures.’
‘So people with different DNA have different cell structures?’ I asked.
‘Absolutely,’ she said. ‘Different DNA produce different-looking people due to slight differences in their architect’s plans. Nearly all the DNA in each person is the same so we all have the same sort of cells — muscles, nerves, skin and so on. We all have two eyes and one nose. It’s just the teeny-weeny differences in the codes which produce our different characteristics, like blue or brown eyes; blondes, brunettes or redheads; black or white skin; short, tall, everything. It’s these minute differences that are distinctive to an individual and it is these differences that allow us to produce a DNA profile which is like a fingerprint, unique.’
Marina was on a roll. ‘I can use restriction enzymes like EcoR1 to cut the DNA strands in this sample into what we call polynucleotides. Then I’ll put them in an agarose gel matrix, a sort of jelly, for electrophoresis. The polynucleotides are charged so they’ll migrate, or move, in the electric field. The amount they migrate is dependent on the size and shape of each polynucleotide. Imagine that the gel acts as a sort of sieve, the bigger the polynucleotide the less distance it will migrate.’
Geoffrey was still nodding. I wasn’t.
‘So in the gel matrix you get separation of polynucleotides into different bands. Then you bake the matrix on to a sheet of nitrocellulose paper to give a permanent pattern of lines where the bands are.’
‘How does that help?’ I was out of my depth here, I thought. Give me a poor jumping novice chaser over Aintree fences any day.
‘Everyone has slightly different DNA so everyone has a different pattern. In criminal cases, they say that the odds of two different people having the same pattern is more than 60 million to one. Unless, of course, you have identical twins. They will have matching patterns because their DNA is exactly the same, that’s what makes them identical. However, what I’m doing wouldn’t be acceptable as evidence in court. The law requires much stricter systems for producing the profile to prevent cross-contamination. This one will be contaminated with my DNA for a start. I’ll have to do another pattern of just my DNA so I can subtract my lines to leave those of our friend alone.’
‘Our friend?’ asked Geoffrey.
‘The door,’ I said.
‘Door? What door?’ Poor Geoffrey was getting very confused.
‘The door Marina walked into, twice.’
‘Ah,’ the penny dropped. ‘Yes, the door, our friend. Good. Well done.’
I wasn’t sure if he understood or not but he seemed happy to wander around the lab as Marina worked away with the fingernails. She then scraped some cells from the inside of her cheek to do another profile of her own DNA alone.
‘It will take several hours now for the polynucleotides to migrate in the gel matrix. We’ll have the results next week.’
‘What will they give us?’ I asked.
‘Nothing on their own,’ she said, ‘but if we get more samples and one of them matches, then, bingo, we have our man.’
‘So all I have to do is go around asking everyone for a DNA sample.’
‘You don’t
‘Is that legal?’ I asked.
‘No. Strictly speaking it’s not,’ she said. ‘The Human Tissue Act makes it illegal to hold a sample for the purpose of producing a DNA profile without the consent of the donor.’ She waved her hand at her work. ‘All this has technically been illegal but I’m not telling.’
‘Me neither,’ said Geoffrey flamboyantly. ‘Doctor/patient confidentiality, don’t you know.’
Marina and I went back to Ebury Street while Geoffrey returned home to Highgate.
‘See you next week to take the stitches out,’ he had said as he got into his Volvo. ‘Take care with that girl of
