It is difficult to determine the sex of very young chickens, but it is easy to tell, by visual observation, whether the feathers are “barred.” The barred pattern is inherited as a sex-linked dominant trait. This trait is used regularly by chicken breeders who receive orders for only male or only female chicks, and must be able to deliver the appropriate sex of very young birds. Determine whether the male and female parents should be taken from normal or barred true-breeding lines in order for the sex of all chicks to be determined at the time of hatching. Show the Punnett square for the mating you select, to confirm that the desired phenotypes result. (Note: In birds, sex is
determined as follows: XX = male, XO = female; only the X chromosome carries sex-linked genes.