Right, second baby has a P K U gene from his mum and a normal gene from his dad and he is not affected, but he is a P K U carrier, right, third baby gets a normal gene from his mum and a P K U gene from his dad and he's the same, or she's the same P K U carrier, but not affected, unfortunately the last baby gets a P K U gene from, from mum and a P K U gene from dad and this baby has got P K U and that is a simple, simple sort of exercise of how genetic disorders sometimes appear and sometimes don't 