A pt. of cystic fibrosis (homozygous) married a carrier (heterozygous). The chances of developing cystic fibrosis in the offsprings is
B. 25% carriers, 75% affected
C. 75% carriers, 25% affected
D. All are carriers
E. All are affected
Ans. A. 50%
carriers, 50% affected
• Cystic fibrosis is an
autosomal recessive disorder. Imprtant featrure of AR disease:
- Either sex affected with
equalfrequency or severity.
- Affected person is homozygous
or compound heterozygote for a-single gene deftet.
- Heterczygous carriers of a
deft ctive allele are usually clinically normal.
- Horizontal pattern ofpedigree
with a single generation affected.
• The chance of developing cystic fibrosis in our question is 50%.
