When Mom’s and Dad’s Genes Clash: New Study Reveals a Genetic Tug-of-War That Shapes Our Health

Scientists have shown that our maternal and paternal genomes can exert distinct — and sometimes opposing — influences on health and disease.

This work, was led by Zoltán Kutalik at the University of Lausanne in close collaboration with Lili Milani’s group (University of Tartu, Estonia) and Stefan Johansson’s group (University of Bergen, Norway).

For decades, genome-wide association studies (GWAS) have identified thousands of genetic variants linked to human health. However, they typically ignored which parent each variant came from, assuming the effects were identical.

“This study challenges that assumption: due to genomic imprinting — where only one parental copy of a gene is expressed — the parental origin of a genetic variant can differentially influence human health” says professor Stefan Johansson, who led the Norwegian part of the study

The team in Bergen contributed with unique data from the Norwegian Mother, Father and Child Cohort Study (MoBa), which began around the year 2000 and has enrolled more than 250,000 Norwegian participants.

Genetic imprint from mother and father

Published this week in Nature the study has two key facets. First, it introduces a scalable method to determine the parental origin of each DNA segment using genetic data from relatives. Second, the newly developed method was applied to three large population cohorts — from the UK, Estonia, and Norway — totaling over 230,000 individuals.

The research team identified more than 30 parent-of-origin effects (POEs), where the impact of a genetic variant depends on whether it was inherited from the mother or the father.

“Many of these parent-specific effects showed ‘bi-polar’ patterns — the same gene variant increasing a trait when inherited from one parent but decreasing it when inherited from the other. This tug-of-war between parental genomes sheds light on a fascinating evolutionary battle,” explains Roya Karimi, postdoctoral researcher at the University of Bergen. 

The genes pull in different directions

The study also points to a plausible mechanism behind these opposing effects: the same genetic variant can simultaneously influence the expression of a maternally- and a paternally expressed gene, pulling traits in opposite directions. This was particularly prevalent for growth (eg. height) and metabolism (eg. type 2 diabetes, triglycerides) related traits.

“This is one of the strongest pieces of evidence yet for the long-standing evolutionary theory of genetic conflict between parental genes,” says Stefan Johansson. “Paternal genes tend to promote offspring growth, even at the mother’s expense, while maternal genes aim to conserve resources for future offspring.”

This study introduces an innovative way to test parent-specific genetic effects on complex traits, uncovers novel loci influencing human health, and provides one of the first pieces of human genetic evidence for the conflict hypothesis.

Link to the publication: https://www.nature.com/articles/s41586-025-09357-5