Title HG CL 6 RISK CALCULATION.pdf ✅

Example 2 : II. Calculation involving age-dependent penetrance
B. AUTOSOMAL RECESSIVE Important key points : Key point 1 Key point 2 Key point 3 Key point 4 Both parents must be carrier : - Parents will child of AR inhr = obligated carriers Carrier risk for siblings : - Prob healthy siblings with AR inhr = 2⁄3 Carrier risk for extended family : - Parents + child of AR = obligated carrier. - 2 nd deg relatives (uncles, nephews) – 50% chance carrier - Each further step – reduce risk by 50% Risk of affected child - Product of prob that each is a carrier x 1⁄4 Mother’s risk x Father’s risk x 1⁄4 Why 1⁄4 ? - Ratio of affected chance in AR inhr. I. Calculation : Example 1 :