New research has found that most of the individual differences, some even related to genetic illnesses such as lupus or schizophrenia, do not depends on the 0.25% variation in coding DNA (genes) but on the quite larger (1-4%) diversity in non-coding regions of the genome (sometimes called "junk DNA"), which nevertheless directly influence how key proteins, known as transcription factors, bind to the actual genes.
In the words of co-researcher Michael Snyder:
... 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.
More details at Science Daily.
Relevant research papers:
- Maya Kasowski et al., Variation in Transcription Factor Binding Among Humans. Science, 2010. Pay per view.
- Wei Zheng et al., Genetic analysis of variation in transcription factor binding in yeast. Nature, 2010. Pay per view.