Please need help answering this question... especially part b, I am really confu

Question

Please need help answering this question... especially part b, I am really confused.

Hurler syndrome is an autosomal recessive disease caused by a deficiency of the enzyme alphaLiduronidase. 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 HardyWeinberg equilibrium. Show your work and express your answer to three significant figures.

b. What would be the increased risk of Hurler syndrome among the offspring of firstcousin matings? Show your work and express your final answer to three significant figures.

Explanation / Answer

Hurler syndrome is an X-linked recessive disorder. Which means that the individual needs 2 alleles for this gene in order to have the disease.

a) The population incidence is 1 in 90,000

Allele frequency: Since every individual has 2 alleles for the gene responsible for Hurler syndrome, and only one in 90,000 individuals is affected by it, the allele frequency is given

as total number of affected alleles/ total number of alleles in the population = 2/180002 =1.111 x10-5

Genotype frequency is the ratio of affected individuals to the total number of individuals = 1/90001 =1.111 x10-5

b) As known, consanguineous marriages are associated with a higher frequency of autosomal recessive disorders and more precisely between first cousins, hence the risk of hurler’s syndrome is higher in offspring of first cousins.

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