The human bone disease osteogenesis imperfecta (OI) is generally caused by an autosomal dominant mutation in a gene (COLIA1) that produces type 1 collagen, a tissue that strengthens bones and muscles and multiple body tissues. People with OI have weak bones, bluish color in the whites of their eyes, and a variety of afflictions that cause weakness in their joints and teeth. However, this disease doesn't affect everyone who has a COLIA1 mutation in the same way - the mutation is about 80% penetrant.
If a person with OI who is heterozygous mates with a person who is homozygous for the wild-type allele, what is the probability that their first child will show symptoms of OI?
Please enter your answer as a number between 0 and 1 rounded to the nearest 2 decimal places.