BBC Correspondent Christine McGourty reports: Secret to good motherhood

Researchers from Cambridge University say they have found a mothering gene in mice.

They investigated a gene called Mest over a period of four to five years.

They mutated the gene in a colony of mice, and found that, when the gene was defective, mothers did not look after their young properly.

BBC Science Correspondent Christine McGourty: Clue to why some women find motherhood difficult

They would not feed or clean them and were slow to retrieve them if they wandered away from the nest.

Children are thought to develop strong psychological bonds with their mothers over the first three years of their lives.

But there is a gene similar to Mest in humans and the team say this could explain why some mothers fail to bond with their babies.

The mother-baby relationship develops in the first three years

Professor Azim Surani, who led the research team, which said: "There is an equivalent gene in humans that shows similar characteristics."

Based on the studies with mice, he said, this would suggest that a woman with a defective gene would have similar problems with children.

Genes usually exist in two copies - one inherited from the mother and one inherited from the father.

But 'imprinted' genes such as Mest need only one copy to have an effect.

Mest is only active when inherited from the father.

Dr Surani discusses his research

Writing in the Nature Genetics journal, the Cambridge researchers say this might be nature's way of ensuring females put full effort into caring for their young.

The research team is studying the action of imprinted genes.