What Are Genes?

Genes are the packets of information within your DNA that hold the instructions for building proteins and running the processes inside your cells. Because almost everything that happens in a cell results from what genes encode and how they are read, it follows that faults in genes can cause problems in cells — and problems in cells can cause disease. That reasoning led researchers in the 20th century to start connecting specific gene changes to specific conditions.

A worked example: sickle cell disease

Sickle cell disease affects millions of people worldwide. It occurs when red blood cells deform into a crescent or sickle shape, making them rigid, prone to becoming stuck in small blood vessels, and broken down faster than normal cells.

Researchers traced the deformation to haemoglobin, the oxygen-carrying protein packed inside red blood cells. A single change in the haemoglobin gene produces a protein that is "sticky" on one side. Those sticky proteins clump into long fibres, and the effect is strong enough to distort the entire cell into a sickle shape.

Sickle cell disease is recessive, meaning it requires two altered copies of the gene — one from each parent. People with a single copy have sickle cell trait: usually no symptoms, but they can pass the gene on. In the UK, all newborns are offered screening, and testing is offered in pregnancy, precisely because knowing carrier status matters for families.

Modern genetic research

Sickle cell is unusually clean — one gene, one change, one clear outcome. Most conditions are far messier, involving many genes each contributing a small amount, interacting with environment and lifestyle.

To study these, researchers use genome-wide association studies: comparing the DNA of large numbers of people with a condition against those without, looking for sequences that appear more often in the affected group. This has produced a substantial library of genetic variants associated with common conditions — heart disease, type 2 diabetes, and many others.

What a genetic risk actually means

If all this sounds like your genes determine your health, that is a misreading — and an important one.

The great majority of DNA variation has little or no effect. A change in a blood-clotting protein rarely causes clots; it might make them marginally more or less likely. Most variants linked to common diseases are carried by large numbers of perfectly healthy people, and they shift risk rather than dictating outcomes.

Two distinctions worth holding on to:

• Rare, high-impact variants — as in familial hypercholesterolaemia or hypertrophic cardiomyopathy — have large effects and genuinely warrant specialist medical follow-up.
• Common, low-impact variants — the type most consumer tests report — each nudge risk slightly. They are interesting and can be motivating, but they are not diagnoses.

Someone who eats well, exercises, does not smoke and keeps their blood pressure in range can live a long, healthy life while carrying variants associated with disease. In most cases, what you do matters more than what you carry.

Things to consider before testing

• Results can have implications for blood relatives, who may not want to know
• A result may cause anxiety, particularly where nothing can be done about it
• Consumer tests screen selected variants — a "clear" result does not rule out risk
• Where a condition is suspected clinically, NHS genetic services with genetic counselling are the appropriate route

Testing with Rightangled

Rightangled's DNA tests examine genetic markers relating to health risk, nutrition and medication response. Results are reviewed by our clinical team, which includes GPhC-registered independent prescribers, with medical oversight from our doctor, Dr Abdullah — so you get realistic interpretation of what a result does and does not mean, rather than raw data.

Verify us with the General Pharmaceutical Council (registration 9011933), see our LegitScript certification, and read reviews on Trustpilot.

Related reading: DNA, the building block of everything.

This article is for general information and does not replace personalised medical advice.