what causes diseases such as cancer, diabetes or obesity? It's possible that genes are the cause. The other probability is that these are related to one's lifestyle. Popularly known as the nature versus nurture debate, it was believed there was a balance between the two. A new study shows that external environment (nurture) has a greater effect than genes (nature). Several epidemiological studies on incidence of diseases are being carried out to find a conclusive answer to how genes and the external environment react with each other.

In the new study, researchers from Princeton University used yeast for their experiment. Yeast is a good model to show how genes work in human beings and give the opportunity to study thousands of gene expression patterns.The researchers used two genetically different strains of yeast from two different environments: one from the laboratory and the other from a vineyard.

The study says that, just like in human beings, a balance exists between genes and environment in yeast, which determines its traits. The interesting part is the expression of many genes in yeast is under the control of other genes. These other genes are almost always affected by the external environment.

The study was published in the April issue of PLoS Biology.