But it is telling that many autistic people have a genetic defect which interferes with their sulphur metabolism.

ECONOMIST: The human microbiome

The vast majority of colorblind people have trouble seeing red or green, due to a genetic defect in the color-sensing cells, called cones, at the back of the eye.

WSJ: New Outlook for Colorblindness

Isis needs one in order to start a large and expensive clinical trial testing its drug in patients who have high cholesterol that is not caused by a genetic defect.

FORBES: Genzyme Eyes Isis Drug

Nowell's research at Penn in Philadelphia was the first to show that a genetic defect could be responsible for cancer, His work has led to numerous discoveries into the growth of cells related to cancers and other disorders.

WSJ: 3 cancer scientists awarded $500K NY medical prize

In recent experiments carried out by Chiara Conti and other members of Dr Bensimon's team, molecular combing was used to identify a genetic defect responsible for cancer of the kidney, which is notoriously difficult to diagnose in its early (and therefore treatable) stages.

ECONOMIST: Let��s get this straight

Gleevec was the first cancer pill targeted at a specific genetic defect.

FORBES: Cancer Vaccine Finds A Proving Ground

These drugs were tested in small patient populations who have a specific genetic defect that the new drug was designed to repair.

FORBES: Is Big Pharma Utilizing Too Many Resources on Potential Blockbusters?

In a potentially historic victory, a drug targeted to a specific genetic defect has improved the ability of cystic fibrosis patients to exhale.

FORBES: Vertex May Make History With Cystic Fibrosis Drug

But the Cystic Fibrosis Trust said the medicine was "transformational", had a "dramatic effect" and that experts say "no other medicine addresses the basic genetic defect in cystic fibrosis".

BBC: Cystic fibrosis: New drug Kalydeco refused for Welsh NHS