• Question: Why do mouse and rat have different DNA?

    Asked by lectureattendee to Hannah on 1 Feb 2019.
    • Photo: Hannah Cornish

      Hannah Cornish answered on 1 Feb 2019:

      Brown rats and house mice are different species that split from their last common ancestor 11 million years ago. The ancestors of rats and mice stopped breeding with each other then, so they stopped sharing DNA. This is probably because those ancestors started living in different places or behaving differently so didn’t come across each other any more. Each species has had 11 million years worth of changes to their genes which means that rat DNA is now quite different to mouse DNA.