While every human being gets two sets of chromosomes, one from the mother and the other from the father - they're not always equally important in determining how we develop.
That's the conclusion of Dr Christopher Gregg, a Human Frontiers Postdoctoral Fellow at the Department of Molecular and Cellular Biology, Harvard University, who studied the roles of so-called "imprinted genes" in brain development, brain function and animal behaviour.
He won the 2010 Eppendorf (a biotech equipment supplier) and Science Prize for Neurobiology for his research, which he described in an essay in the journal Science, published last week.
Human beings inherit 23 chromosomes from each parent, and they pair up and combine to form the thousands of genes that control every aspect of our biological development - from height to hair colour.
But, for reasons that aren't entirely clear, in some genes the DNA from one parent suppresses the DNA from the other parent, selectively controlling the expression of that gene. The process is called "genomic imprinting", and it may significantly influence our biological development - possibly making us more susceptible to diseases like autism.
Gregg and colleagues used so-called "next generation" sequencing technology to sequence the genomes of the brain regions of mice, looking for imprinted genes, and then determining whether the genes were under the influence of maternally or paternally derived DNA.
They found there were differences in the expression of genes in different stages of development of the mice brains, in different cell types, and in different brain areas.
In mouse embryos, imprinting was more likely to be maternally-influenced, whereas in adult mice, it was more likely to be paternally influenced.
Links to depression, schizophrenia and autism
Imprinted genes were more likely to be found in the genes that code for certain types of brain tissue. They were more common in genes coding for the major monoaminergic nuclei of the brain, ie those neurones (nerve cells) that manufacture neurotransmitters such as serotonin, dopamine, or noradrenaline.
These areas of the brain have been implicated in a wide range of neurological and psychiatric disorders, including major depression, eating disorders, schizophrenia, and autism spectrum disorders, writes Gregg.
Past research by others has shown imprinted genes coding for the cortex and limbic areas of the brain tend to be maternally influenced, while those coding for the hypothalamic regions tend to be paternally influenced, he writes.
Just why some genes should be selectively under the control of one parent's DNA at the expense of the other isn't known, although there are theories that it may confer some (as yet unknown) evolutionary advantage, in ensuring one parent's DNA survives at the expense of the other's.
The downside is that imprinted genes may make an individual more vulnerable to disease, writes Gregg. If an imprinted DNA from one parent suppresses the other parent's DNA, but itself contains mutations, there will be no functional back up DNA from the other parent, and so the entire gene may be defective and give rise to disease. Gregg suggests that diseases like autism and schizophrenia may be associated with imprinted genes that contain mutations.
Associate Professor Thomas Preiss from University of New South Wales is Acting Head of the Molecular Genetics Division at Victor Chang Cardiac Research Institute. He says the study of genomic imprinting, also known as epigenetics, is a fast-growing branch of molecular biology that is becoming increasingly important in the study of the causes of cancer.
He says that genomic imprinting may have an evolutionary function.
"It may be one mechanism that populations have of adapting to changing environments", he says.