question archive Hurler syndrome is an autosomal recessive disease caused by a deficiency of the enzyme alpha-L-iduronidase
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Hurler syndrome is an autosomal recessive disease caused by a deficiency of the enzyme alpha-L-iduronidase. Affected individuals are mentally retarded, and they have skeletal abnormalities and short stature. The population incidence is about 1 in 90,000.
a. Calculate the allelic and genotypic frequencies for the disease assuming Hardy-Weinberg equilibrium. Show your work and express your answer to three significant figures.
Answer:
b. What would be the increased risk of Hurler syndrome among the offspring of first-cousin matings? Show your work and express your final answer to three significant figures.
Question: A.
Representation:
· Genotype for individuals with Hurler = hh = recessive homozygous condition.
· Normal individuals, will have genotypes:
· HH = Homozygous dominant
· Hh = Heterozygous dominant
Genotype:
· Total population = 90,000
· Since 1 out of 90,000 individuals in the population have Hurler disease, genotype frequency of aa = q2
· Genotype frequency for aa = q2 = 1/ 90000 = 0.0009
Allele frequency for q = 0.03
As per Hardy-Weinberg equilibrium p+q = 1
Thus, p = 1- 0.03 = 0.97
Genotype frequency for AA = p2= (0.97)2= 0.9409
Answer:
Allele frequency of disease = 0.03
Genotype frequency of disease = 0.97
Question: B.
· For first cousin, coefficient of relationship or proportion of diseased genes shared = 1/8.
· The diseased gene in the offspring = ½
· Thus, coefficient of inbreeding for first cousin mating = 1/16
· The allele frequency in this case = q= 0.03.
· Risk of disease = q x 1/16 = 0.03/ 16 = 0.001875