Recent research has indicted that the role of genes is much more complex than we thought.
"People talk about an individual’s genome as if it was a single
consistent entity—but it isn’t. Every one of us actually contains a cosmopolitan melting pot of different genomes. Our 37 trillion or so cells
all arose from a single fertilized egg, and as this progenitor divided
again and again, its daughters picked up mutations in their DNA that
distinguished them, and their descendants, from their neighbors.
can now detect the subtle differences between these dynasties and trace
their lines of ancestry. That is, they can reconstruct the genealogy of
a single body. And they’re finding that these family trees are more convoluted than anyone suspected...."
This article further explores some recent research with links to the original work.
“The assumption has always been that the genomes within every
individual are identical,” says McConnell. “Now that we know that
assumption is false, it's forced a rethink.”
For example, many
neurological disorders like schizophrenia run strongly in families, but
large studies have identified genes that explain just a small fraction
of this heritability. Maybe that’s because “we’ve been looking at blood
genomes to understand brain genomes,” says McConnell. By analyzing DNA
taken from blood samples, we’re missing a lot of the important mutations
that are hidden in neurons themselves—or in specific pockets of
neurons. “Maybe the missing heritability lies in these brain genomes.”
Here is another review of recent research:
And here are some of the original scientific articles: