Question: why would the mothers gene effect the offspring?

Darren Logan answered on 13 Mar 2012:

The most obvious way is because you get half your genes from your mother and half from your father. So if a mother has a gene that doesn’t work properly, there is a 50% chance the offspring will have that gene too. However, even of the offspring doesn’t get a faulty gene, it can still be affected by its mother’s genes.

Here is an example: we have a mouse that has a particular faulty gene. In general, the mother seems ok and doesn’t seem ill in any way. But then we noticed that when she had litters of babies, many of them didn’t seem to surive very long. We we watched carefully, we found that the mothers with the faulty gene did not look after their babies properly, while the mothers with the normal gene did. It didn’t matter what genes the babies had, it was the gene of the mother that made the difference. Since genes can be involved in behaviour, if you change a gene you can change a behaviour. If this behaviour is mothering, then the effect will be seen most on her offspring.