In: Biology
Tay-Sachs is an autosomal recessive disorder that results in progressive loss of brain tissue Jewish settlers and is engaged to Howard. Maria and Howard are concerned about having children since one of Maria’s uncles on her mother’s side had died from Tay Sachs. Howard’s family is of Scandinavian origin has no record of Tay Sach. You are asked to advise Maria and Howard as to the risk of them having a child with Tay Sachs. (FYI, the incidence of Tay Sachs in eastern European Jews is about 1/1000 and in other populations about 1/100,000). Construct a pedigree appropriate for this family and calculate the estimated risk for Maria and Howard to have a Tay-Sachs child.
Please show any calculations
Given Tay-Sachs is Autosomal Recessive disorder that results in loss of brain tissue in Jewish settlers.
So, let the dominant allele = A = free from disorder ; a = recessive allele= disease causing only in Homozygous condition only.
Maria and Howard are concerned about having children as Maria's uncle on her mother's side died because of Tay-Sachs. Maria is a Jewish settler. So, her Genotype could be AA or Aa as she is not affected so she can be a carreir or free from the disorder allele.
Howard's family is of different origin and had no record of Tay-Sachs. So, he is free from the disease and is of Genotype = AA.
Given, the incidence of Tay-Sachs or rate of occuring the disease in eastern Europe jews = 1/1000 ; while in other population = 1/ 100,000.
Maria is Jewish so she can have the disorder (allele) by = 1/1000
Howard is of different origin or say other population so rate of occuring = 1/100,000.
Pedigree and their possible Genotypes and probabilities are in image below :
Probability or Risk that their child will have Tay-Sachs =
Probability of Maria = 1/1000 * 1/2 ( 1 = have allele ; 2= have Allele + do not have Allele)
= 1/2000
Probability of Howard = 1/100,000 * 1( do not have family history of Tay-Sachs, so considered free from recessive allele).
= 1/100,000 * 1
= 1/100,000
Total Probability or Probability of child with Tay-Sachs=
1/2000 * 1/100,000
= 1/2 * 10^8
= 1/2 * 10^(-8)
= 0.5 * 10^(-8)