i had a request from a deaf coup, herred tarial deaf, and they wanted deaf. they wanted to create a child that was deaf like them. there's a separate question, can you use genetic testing if it makes the child worse off or less than it might have been. my answer is no. so many questions being raised, none more than this without news of people in britain, looking into the possibility of parents being 3-parent. >> remember your high school textbook where the cells are dividing. it takes power. you need energy. there's a mitochondria, the battery park, the energy factory. when they are not right, the battery doesn't work. you get diseases if it's not right. we can take the mitochondria from a normal egg and put them into an egg from the woman who has the condition. fertilise that. you have prepared - thing of it like an organ transplant. we transplant the mitochondria. to me just because you have a power pack doesn't make parent? >> opponents are up in arms. one of the things they are raising is there's no way of knowing what the consequences have been. could th