BBC News

Thursday, April 8, 1999 Published at 21:42 GMT 22:42 UK

Genetic battle of the sexes

Absence of the good mothering gene meant the mice did not build nests

The two sexes are engaged in a battle to try to guarantee that their genes are passed down the family line and fathers seem to have the advantage, according to new research.

The discovery is of a new gene in mice for good mothering. Ironically, this is inherited from the father.

Mothers without the gene do not nurture their offspring well and only eight per cent of the babies survive. Over 83% of the babies born to mothers with the gene live beyond weaning.

As this is at least the second such gene, evidence is growing that males pass on certain genes to help ensure that their daughters take good care of their grandchildren.

Survival of the fittest

The reasoning is that mothering is an exhausting business and so to try and ensure the survival of her genes, a mother would be better leaving her offspring earlier and spending the energy on breeding again.

But fathers stand to gain if the mothers care for the offspring for longer, increasing the children's chances of survival.

The scientists in Cambridge, UK and Tokyo, Japan showed that the Peg3 gene is crucial for mouse mothers to care for their babies. In September 1998, the same group showed that a gene called Mest, producing a very different protein, had a similar effect.

[ image: Human genes could work in the same way]
Human genes could work in the same way
One of the team, Dr Samuel Aparicio at Cambridge University, told BBC News Online that there are analogues of these genes in humans. He says it is "a very obvious possibility" that they serve the same purpose in people.

"The interest is always to look and see whether this tells us anything about human behaviour or conditions such as mother-baby bonding. For example, one might want to look at this gene as candidate for post-natal depression."

But Dr Aparicio points out that: "Maternal behaviour is a very complex phenomenon. Not just behaviourally, but it is integrated through the parts of the brain we do not know much about and it also is affected by environmental factors."

Mothers may fight back

The research reveals the importance of "imprinted genes" as a weapon in the battle of the sexes. Copies of these genes are passed on by both parents to their offspring, but only one copy is active.

For the Peg3 and Mest genes, it is the father's copy, giving him some control over the destiny of his family tree.

However, the battle may well not be one-sided. Mothers can pass on active imprinted genes but as yet scientists do not know what effect these have on their male offspring.