How is muscular dystrophy passed down to a child from his parents?

X linked or new mutn. The md's can arise as a new mutation in a child or an asymptomatic carrier mother on one of her x chromosomes. As a recessive gene, it will not express when balanced by a normal gene, but can express in male offspring since a carrier x is paired with a y. If mom is a carrier, there is 50% risk with any male pregnancy to have an affected male.