Humans inherit their genetic makeup equally from their parents. But new research from the University of North Carolina finds that all mammals are more like their fathers genetically because they use more of the DNA that was inherited from him.
The study is published in the journal Nature Genetics.
The researchers say it's an important finding for learning about disease because scientists typically don't take into account whether a mutation came from the mother or the father. It matters, though, because the consequences will depend on who contributed the genetic variant.
Mutations are thought to result from copying errors in cells.
Senior author Fernando Pardo-Manuel de Villena, professor of genetics, predicted in a written statement that the finding would open doors to "entirely new areas of exploration in human genetics."
He said the scientific community has known about 95 genes that have a parent-of-origin effect, called "imprinted genes." How they play out in disease depends on whether the mutation was mom's or dad's. But the new research shows that thousands of other genes also have a "parent-of-origin effect."
According to study background material, the UNC research team used three genetically diverse inbred strains of mice to create nine different types of hybrid offspring. When the mice were grown, they measured how much gene expression came from the mother and the father for every single gene.
"We found that the vast majority of genes — about 80 percent — possessed variants that altered gene expression," said first author James Crowley, assistant professor of genetics. "And this was when we discovered a new, genome-wide expression imbalance in favor of the dad in several hundred genes. This imbalance resulted in offspring whose brain gene expression was significantly more like their father's."
UNC has the most genetically diverse mouse population for research in the world. It also can create mice with the level of expression desired for any gene, so it can look at specific diseases, the researchers said.
"This expression level is dependent on the mother or the father," Pardo-Manuel de Villena said. "We now know that mammals express more genetic variance from the father. So imagine that a certain kind of mutation is bad. If inherited from the mother, the gene wouldn't be expressed as much as it would be if it were inherited from the father. So the same bad mutation would have different consequences in diseases that were inherited from the mother or from the father."
This adds to a growing body of information on how genetic mutations pass from fathers and mothers. In 2012, Nature reported on a study of Icelandic families that showed fathers pass on more mutations as they get older.
"By starting families in their thirties, forties and beyond, men could be increasing the chances that their children will develop autism, schizophrenia and other diseases often linked to new mutations," wrote Ewen Calloway.
That study noted that fathers passed on nearly four times as many new mutations as did mothers. They tracked it by comparing a child's genetic makeup to that of both parents, looking for mutations the parents lacked, then determining who contributed each.
Scientists at the University of Cambridge have suggested that teenage parents may be more likely to pass on birth defects to their children.
A different study said teenage fathers also pass on a lot of mutations, maybe 30 percent more than fathers in their 20s, "which may explain why the children of younger parents have been found to have a higher risk of disorders such as schizophrenia, autism and spina bifida," according to The Independent.
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