Genetic defects can always be passed on but some defects in chickens are due to the way they are incubated. I got an Orloff chick that both feet had all the toes turning in. At first the chick couldn't stand but I helped the chick to drink and eat and stand it's first two days. On day 3 the chick started to stand on it's own and I placed the feed and water a little distance so that the chick had to walk to get to food and water. I made sure many times a day the chick was able to do it and excersize the feet. Now you'd never know anything was wrong. For that I would say the chick was in an odd position in the shell. For a genetic defect definetly you wouldnt' want to breed it but as long as it's not suffering or in pain I have always kept them. I have a blind Wyandotte now that is 3 that does fine with some extra help. I used to raise zebra finches and they have all sorts of baby leg problems and I always had one handicapped bird at any given time. If you can just give the little extra that they need they can usually get along fine. A good thing to do is not to baby your chick- get him out and using the toes. As long as all else is healthy, he can eat, drink and poo fine than he/she will probably do fine. The extra excersize on the legs does do wonders to help birds straighten up as well.