How can we use Hardy-Weinberg equilibrium to calculate carrier frequencies of recessive diseases if we know the proportion of people who are affected?. Helen Stuart, Cardiff. Essay plan. Description of Hardy-Weinberg principle (HWP) Allele frequencies: p+q=1
How can we use Hardy-Weinberg equilibrium to calculate carrier frequencies of recessive diseases if we know the proportion of people who are affected?
Helen Stuart, Cardiff
i.e. square root of q2
Tay Sachs disease affects 1 in 3,900 Ashkenazi Jews. What is the expected frequency of carriers?
q2 = 1/3,900
q = square root of 1/3,900 = 1/62
p+q=1 so: p+1/62=1 so: p=61/62
Carrier frequency (2pq) = 2 x 61/62 x 1/62
= approx 1/31 in Ashkenazi Jewish population
Red-green colour blindness has an incidence among males of 1/12 (8%). What is the expected frequency of female carriers?
For X-linked disorders, the affected genotype frequency is q (not q2 as for recessive conditions).
So, q= 1/12
p+q=1 so: p+1/12=1 so: p=11/12
Female carrier frequency (2pq) = 2 x 11/12 x 1/12
= approx 22/144 (approx 1/8 or 15%)
A pregnant African-American couple presents concerned about their risk of having a child with sickle cell anemia (SSA). The husband has a sister with SSA, and the wife has no family history for SSA. Neither have been tested for SS-trait (SST). The disease occurs in 1 in 576 live born African-American children. Calculate this couple’s risk of delivering a baby with SSA. Hint: The square root of 576 = 24