On the side, he took part in an international workshop studying the human leukocyte antigen gene complex, which helps regulate the immune system.

FORBES: Magazine Article

The system is complex: Each gene is thought to produce, on average, five separate substances, mostly proteins, and these products interact with each other.

WSJ: Genes May Link Disparate Diseases

If successful, this would be "the first example of a gene for a complex disease leading to a drug in the clinic, " says Stefansson.

FORBES: Magazine Article

Gene therapy could be the most complex biologic of all, reckons Dr High.

ECONOMIST: The prospects for using genes as a therapy may be improving

At this point, a woman can undergo the more complex genetic test to confirm the presence of the mutated gene.

BBC: DNA spiral

Alzheimer's is probably caused by a complex interaction of many genes, and it is possible those with the APOE4 gene are less able to repair their injured brains.

FORBES: Magazine Article

But he said that the reasons for humans becoming addicted to any drug were more complex than simply their genetic make-up, and that a test for any gene uncovered by further research would not necessarily work.

BBC: NEWS | Health | Key differences in addicts brains

Usually with a complex disease there are so many genes with a small contribution, but this is a major gene.

BBC: Asthma gene discovery brings hope