Twins in Myanmar

Understanding the links

How do researchers tease apart genetic and environmental factors?

Before the genome era, twin studies helped researchers to assess the relative influences of genes and environment – without knowing details of particular genes. Researchers can record what happens to lots of pairs of identical twins and similar numbers of non-identical, same-sex twins when each pair is raised together in a similar environment. If a characteristic differs more in non-identical twins, this is likely to be because of some genetic effect.

Better, but more difficult to arrange, is to look at identical twins who have been raised in different households (and, therefore, different environments). If they nevertheless turn out very alike, the likeness will be at least in part because of genes shaping their development.

Identifying the genes involved requires a different kind of study. For example, Professor Nick Wareham at the UK Medical Research Council’s Epidemiology Unit in Cambridge is leading a study to understand the complex effects of diet, exercise and other behaviours on the risk of developing type 2 diabetes and how this risk is modulated by genes.

The researchers are using a mega-database of 350,000 people across Europe, which was assembled for a study of diet and health that was originally designed to investigate causes of cancer. The records are so detailed that the Cambridge team have been able to pull out 10,000 people with diabetes and match them with 10,000 diabetes-free controls. This sample is large enough to give good indications of which genes and lifestyle differences are important contributors to diabetes risk, and the results could feed into health policies for tackling what is becoming one of the most common conditions of middle age.

Several studies have already been published as a result of this work. One 2014 study, for example, supported the idea that eating a lot of meat increases your risk of type 2 diabetes, and a 2012 study found that people who drank four cups of tea a day were 16 per cent less likely to develop the condition than people who didn’t drink any.

The researchers are also carrying out genetic analyses using blood samples from the original cancer study. Indeed, there could be scope to use the results to develop population-based interventions and campaigns, where preventative strategies can be targeted at the subgroups most at risk of particular conditions.

Lead image:

Twins in Myanmar

Dietmar Temps/Flickr CC BY NC ND


About this resource

This resource was first published in ‘Genes, Genomes and Health’ in January 2010 and reviewed and updated in December 2014.

Genetics and genomics, Medicine
Genes, Genomes and Health
Education levels:
16–19, Continuing professional development