That could mean there is a genetic difference that determines whether the vaccine works, and that an assay might measure how effective the vaccine is in a particular patient.

FORBES: A Tough Day For AIDS Prevention

"There's only a 1.4% difference in genetic material between humans and chimpanzees, " Sonya Hill, a research officer at Chester Zoo, points out.

BBC: Animal behaviour in the boardroom

But there was no difference in the genetic profiles of those who had and did not have the syndrome.

BBC: Pregnancy danger gene identified

The fish reaches maturity more quickly than its natural cohorts but the genetic change confers no detectable difference in its appearance, ultimate size, taste or nutritional value.

FORBES: Good Riddance To Obama's Regulatory Czar

The difference, however, is not necessarily genetic.

FORBES: Race-Based Medicine, Genomics And You

Dr Skuse's results suggest a systematic difference between male and female behaviour that is under genetic control.

ECONOMIST: Genetics and behaviour

Gilles Tremblay, PhD, a social work professor from Quebec City told the APA that when you look at the difference in life expectancy between men and women, while one year is biological, or possibly genetic while the rest is cultural.

FORBES: Why Do Men Die Earlier? (Hint: It's Not The Ladies' Fault)