Martin Bobrow

"Where people worry is when you get to the brain, the germ cells and the sentinel features that help people recognize what is a person, as opposed to a rat or a rabbit. Things like skin texture, facial shape, speech, replacing brain cells with human cells, allowing the development of human germ cells in animals. And particularly where there is any possibility of fertilisation within an animal."

"Changing animals by putting human genes or cells into their structure is one way of making them more resemble the bit of the human condition you're interested in studying."