Question

Two normal parents have a child with cystic fibrosis. Would this be an autosomal dominant or autosomal recessive disorder? What is the chance that their next child will have cyatic fibrosis?

Answer 1

Cystic fibrosis is an autosomal recessive disorder that damages the lung and digestive system. This disease is inherited when the offspring recieves the gene for cystic fibrosis from both the parents means it occurs when gene for cystic fibrosis occurs in homozygous (recessive) condition. Cystic fibrosis affects the cells that produce mucus, sweats and digestive juices and thickens the secretion and thus block the tubes, ducts and passages.

There will be 25% chance that their next child will have cystic fibrosis.

Both parents are normal heterozygous because their first child has cystic fibrosis. If both or single parent were homozygous (dominant) normal, then their first child would not have cystic fibrosis.

Aa/Aa	A	a
A	AA	Aa
a	Aa	aa (cystic fibrosis)