"We are rapidly entering a time when nearly anyone can have his or her genome sequenced," said Professor Dr Michael Snyder, chair of genetics at Stanford.

"However, the bulk of the differences among individuals are not found in the genes themselves, but in regions we know relatively little about."

"Now we see that these differences profoundly impact protein binding and gene expression."

Genes vary by only about 0.025 per cent across all humans.

Scientists have spent decades trying to understand how these tiny differences affect our development.

Yet non-coding regions of the genome -- which account for approximately 98 per cent of our DNA -- vary in their sequence by 1 to 4 per cent.

Professor Snyder and his colleagues have found that unique changes among individuals in the sequence of DNA affect the ability of transcription factors to bind to the regions that control gene expression.

As a result, the subsequent expression of nearby genes can vary significantly.

"People have done a lot of work over the years to characterise differences in gene expression among individuals," said Professor Snyder.

"We're the first to look at differences in transcription-factor binding from person to person."

"These binding regions or chunks vary among individuals and they have a profound impact on gene expression."

Two individual studies were conducted that compared the binding patterns of transcription factors in chimpanzees and yeast respectively.

"We conducted the two studies in parallel and found the same thing," Professor Snyder said.

"Many of the binding sites differed."

"When we mapped the areas of difference, we found that they were associated with key regulators of variation in the population."

"Together these two studies tell us a lot about the so-called regulatory code that controls variation among individuals."