A couple named Bob and Mary, neither of whom have cystic fibrosis, have three children: Adam (male), Angela (female), and Arnold (male). Arnold has cystic fibrosis, a disorder that arises from two recessive alleles of the cystic fibrosis transmembrane receptor (CFTR) gene. Adam and Angela do not have cystic fibrosis. Mary has one sister named Rose. Rose does not want to undergo genetic testing but her husband Tim knows that he does not have the recessive allele of the CFTR gene. Genetic tests have revealed that Bob’s father Dan has the recessive allele but he does not have cystic fibrosis, and Bob’s mother Diane does not have the recessive allele. Mary’s father Charlie does not have the recessive allele and Mary’s mother Candie died in her late 80s of skin cancer before she could undergo genetic testing, but she did not have any symptoms of cystic fibrosis.
Question 1
Part 1