Genetic testing: should you do it?

In recent years, the market of personalised genetic testing has emerged thanks to cheaper sequencing techniques. Some companies now offer genetic tests at an affordable price (£125 on All that is needed is a mouth swab that can be done at home. Send the box by post and receive the results within a few weeks. Find out about the probability of you developing diabetes, hypertension and dementia and take measures to prevent these diseases. Find out now whether you are one of those unfortunate people who will develop Huntington’s disease in their late years and plan your life accordingly. Why is this technique not used in any healthcare system yet? What are a hundred pounds compared to all the benefits promised by this test?
First of all, how reliable are the predictions made by the test? Given that we are dealing with increased risks, what is their magnitude and reliability? The genetic risks have been calculated in an initial population. Will they be the same in a new population? We should not remember that we are talking about predisposition and that in no case does one genetic variant always cause a disease. Secondly, once I know that I am at risk of diabetes, will I change my behaviour and lead a healthier lifestyle? Shouldn’t everyone eat healthily, exercise, avoid smoking and drink alcohol in moderate amounts? After all, healthy habits are beneficial for everybody. A recent study has shown that communicating genetic risks of disease does not reduce risky health behaviour (Hollands et al.). What is more, if a risk of incurable disease is communicated, like in the case of Huntington’s disease, imagine the unnecessary distress and sense of powerlessness that you might suffer. Thirdly, in case you are more sensitive to a drug but your healthcare system does not deal with it, what can you do with that information? Most healthcare systems in the world do not even take into account sex and weight when administering drugs, let alone genetic sequence. They do, however, adapt the treatment of breast cancer patients or leukaemia patients to their genome because the evidence of the genetic influence is very strong. Finally, do you really want to give your genetic code away? Isn’t your genetic code something special, that belongs only to you and should not be breached lightly? If you have no issue with disclosing your blueprint to anyone, what about sharing it with a health insurance company? Wouldn’t it be risky to leave your genomic sequence out there, prone to being stolen? One must admit that the probability of your data being disclosed to a health insurance company is higher than a health insurance company stealing a bit of you and sequencing you without your consent. In Switzerland and under certain conditions, health insurers can demand the results of a genetic test to be disclosed only if a test has already been carried out. In no case can a health insurance company demand from a patient to carry out a genetic test (Federal Law on Human Genetic Analysis, 2004). In case an insurance company discovers you are at a higher risk of certain diseases, they will want to charge you more for an insurance or will add reserves in the contract. It is in your interest to not deal with your genetic sequence lightly.
In conclusion, you need to ask yourself all these questions before going ahead and getting sequenced. If you deem the advantages to be higher than the downsides, then get yourself tested. I, personally, wouldn’t.

Cristian Riccio


Area under a curve

The following code illustrates the concept of integration. The concept is to divide the x-axis in segments of equal width. We then take the value of y of the function on the right side of the segment and draw a rectangle of height y. The sum of the areas of the rectangles is greater than the area under the curve and approaches the area under the curve when the width tends to 0.

Making agar bridges for electrophysiology


  • agarose
  • potassium chloride (KCl; MW = 74.54 g/mol)
  • glass capillaries
  • ethanol burner
  • syringe


  1. Prepare bent capillary tubes. Alight an ethanol burner by dipping the wick in EtOH, e.g. filling a 1.5 ml tube (eppendorf) with ethanol and dipping the wick in it. Hover the capillary (at 1/3 of its length) over the fire and keep pushing on the short end with a pen until the capillary is bent at a right angle.
  2. Prepare a 20 ml solution at 1% agarose. Weight 0.2 g agarose and dissolve it in 20 ml ddH2O in a 50 ml Falcon tube.
  3. Weight the appropriate amount of KCl in order to achieve a final concentration of 3 M. I need:
    0.020 l x 3 mol/l = 0.06 mol KCl
    0.06 mol x 74.54 g/mol = 4.4724 = 4.47 g KCl

  5. Microwave the agarose solution.
  6. Add the KCl and dissolve it.
  7. Aspire the solution with the syringe.
  8. Fill bent capillary tubes with the solution. Tip: hold the connection between capillary and syringe in order to prevent the mixture from spilling around the capillary. Quickly dry capillaries. Trim the ends of capillaries with a diamond cutter.
  9. Capillaries should not contain any bubbles.


    Store the capillaries, i.e. agar bridges, at room temperature in a 3 M KCl solution.


Day 1: split cells

Matrigel 6 cm diameter Petri dishes:

  • Dilute matrigel 100-fold with DMEM without any additives
  • Pipet 3 ml of diluted matrigel on a 6 cm diameter Petri dish
  • Incubate for 30 min at 37°C

During the incubation, trypsinise a T75 flask of GLUTag cells and resuspend them in 10 ml medium (50/50 fresh/conditioned media).
Remove the matrigel from the dish and add 4 ml full DMEM medium.
Add 2.5 ml of the resuspension in the dish and incubate overnight at 37°C/5% CO2.

Day 2: transfect cells using Lipofectamine-2000

  • 1 hour before transfection, replace the full DMEM medium. Don’t forget to warm the medium in the 37°C water bath.
  • Prepare the plasmid and Lipofectamine-2000 seperately in OptiMEM. Use 3 ug of plasmid and 12 ul of Lipofectamine-2000. Eg. if the plasmid concentration is 1.5 ug/ul:
    1. Pipet 298 ul OptiMEM in a 1.5 ml eppendorf tube labelled “P” (“P” stands for “plasmid”)
    2. Pipet 288 ul OptiMEM in a 1.5 ml eppendorf tube labelled “L” (“L” stands for “Lipofectamine-2000”)
    3. Pipet 2 ul pDNA in the “P” tube.
    4. Pipet 12 ul Lipofectamine-2000 (straight from the fridge) in the “L” tube. Do not mix the lipofectamine-2000 by pipetting up and down. Lipofectamine is sticky and will stick to the pipette if this is done!
  • Let the two tubes sit for 10 min in the hood.
  • Add the tube “P” content to the tube “L” (never do the reverse, the less you pipette Lipofectamine-2000, the better)
  • Incubate for 20 min in the hood
  • Add the 600 ul mixture to the 6 cm diameter dish dropwise.
  • Incubate overnight at 37°C/5% CO2.

Transfer transfected cells into smaller recording dishes

This step is necessary in order to go from a confluent layer of cells to single cells scattered on a dish that are amenable to being patch-clamped.

  1. Warm up medium, PBS and trypsin in the water bath.
  2. Wash cells with 10 ml PBS.
  3. Trypsinise for 3-5 minutes with 2 ml trypsin.
  4. Stop trypsinisation using 6 ml DMEM.
  5. Triturate 30 times.
  6. Centrifuge on a table-top centrifuge at 700 rpm for 5 min at room temperature.
  7. Throw away supernatant (this step gets rid of the trypsin)
  8. Resuspend in 10 ml DMEM and triturate 30 times.
  9. Transfer 5 ml in a new tube and add 45 ml DMEM.
  10. Pipet 2 ml in 3.5 cm diameter dishes for patch-clamp experiments the following day.
  11. Each dish contains 0.5 x 2/50 = 0.5 x 1/25 = 0.5 x 0.04 = 0.02 = 2 % of the initial cells. It is advisable to make another two-fold dilution to get 1% of the initial cells on a few dishes in case the former dilution is not strong enough.

Day 4: patch-clamp

Intracellular (pipette) solution for whole-cell patch-clamp

This solution will be in dialysis with the cytosol and hence is similar to it in composition (high potassium and low sodium).

Chemical mM MW/concentration for 100 ml
KCl 107 74.55 0.7976 g
CaCl2 1 1 M 100 ul
MgCl2 7 1 M 700 ul
EGTA 11 380.35 0.4183
HEPES 10 238.3 0.2383 g
Na2ATP 5 569.16 0.2846

Adjust to pH to 7.2 using potassium hydroxide (KOH).

Always check the molecular weight on the bottles of the chemicals. It may vary, due to different water contents for example.


Chimerel et al., Bacterial metabolite indole modulates incretin secretion from intestinal enteroendocrine L cells, Cell Rep., 2014
Link to the article in PubMed

Extracellular (bath) solution for whole-cell patch-clamp in GLUTag cells

This solution is needed to keep cells in a physiological environment during patch-clamp experiments. It also contains glucose as a nutrient.

Chemical mM MW/concentration for 1 L for 500 ml for 500 ml 10X
NaCl 138 58.44 8.065 g 4.0325 g 40.325 g
KCl 4.5 74.55 0.335 g 0.1675 g 1.675 g
NaHCO3 4.2 84.01 0.3528 g 0.1764 g 1.764 g
NaH2PO4 1.2 120 0.144 g 0.072 g 0.72 g
CaCl2 2.6 1 M 2.6 ml 1.3 ml
MgCl2 2.6 1 M 1.2 ml 0.6 ml 6 ml
HEPES 10 238.3 2.382 g 1.1915 g 11.915 g

Glucose: 1 mM (18 MG/100 ml)
pH 7.4 using NaOH
For a 500 ml 1X solution, I added 2.4 ml of NaOH at 1 M concentration.

Add CaCl2 and adjust the pH when the solution concentration is 1X.
Add glucose to the solution needed on the day, usually 50 ml.

Always check the molecular weight on the bottles of the chemicals. It may vary, due to different water contents for example.


Rogers et al., Electrical activity-triggered glucagon-like peptide-1
secretion from primary murine L-cells, J. Physiol., 2011
Link to the article in PubMed

Culturing GLUTag cells

Starting point: confluent T75 flask containing stuck GLUTag cells and 20 ml DMEM medium

All steps are undertaken in a hood!

Day 1: Splitting a confluent flask

  1. Label one 50 ml falcon tube with “condition” and one with “rubbish”
  2. Transfer the DMEM from the flask into the falcon labelled “condition”
  3. Wash cells with 10 ml PBS and transfer the dirty PBS into the “rubbish” tube
  4. Add 3 ml trypsin to the flask and leave it in the incubator for 3-5 min
  5. Check under the microscope that the cells have detached
  6. Add 5 ml fresh medium to stop the trypsinisation reaction
  7. Spin the cells down at 600 rpm for 5 min
  8. Chuck the supernatant
  9. Resuspend the cells in 5 ml fresh medium and triturate them 20 times with a 5 ml stripette (Note: using a 5 ml stripette rather than a bigger-volume one will help separate the cells due to the narrower aperture of the pipette)
  10. Add 5 ml condition medium from the “condition” tube to the resupsended cells
  11. Add 3 ml of the resuspension to a new T75 flask containing 17 ml fresh DMEM medium
  12. The other 7 ml can be used to seed Petri dishes for use in experiments, e.g.: calcium imaging, electrophysiology, secretion experiments, transfection, etc.

Day 3: Changing medium

Exchange 10 ml supernatant for 10 ml fresh DMEM medium

Day 5: Splitting a confluent flask

Refer to Day 1.

Cristian Riccio, Institute of Metabolic Science, University of Cambridge


Thanks to Dr. Edward Emery and Dr. Frank Reimann from the Institute of Metabolic Science for their contribution to the establishment of this protocol.