Tay-Sachs is a recessive lethal disease in which there is neurological deterioration
early in life. This disease is rare in the population overall but is found at relatively high
frequency in Ashkenazi Jews from Central Europe. A woman whose maternal uncle had the
disease is trying to determine the probability that she and her husband could have an affected
child. Her father does not come from a high risk population. Her husband’s sister died of the
disease at an early age. a. Draw the pedigree of the individuals described. Include the genotype
where possible. b. Determine the probability that the couple’s first child will be affected.
Solution
Maternal Grandmother: Nt Maternal Grandfather: Nt Uncle: tt Mother: NX Father:
NN Woman: NX Husband\'s mother: Nt Husband\'s father: Nt Husband\'s Sister: tt Husband:
NX t = tay sachs X = unknown N = Normal gene There\'s a 50% chance the woman is a carrier
and a 66.6% chance the husband is a carrier. Going by what we know, there is a 1 in 12 chance
the child will have the disease. (24 total outcomes, only two result in the child having tay sachs).
Tay-Sachs is a recessive lethal disease in which there is neurologic.pdf
1. Tay-Sachs is a recessive lethal disease in which there is neurological deterioration
early in life. This disease is rare in the population overall but is found at relatively high
frequency in Ashkenazi Jews from Central Europe. A woman whose maternal uncle had the
disease is trying to determine the probability that she and her husband could have an affected
child. Her father does not come from a high risk population. Her husband’s sister died of the
disease at an early age. a. Draw the pedigree of the individuals described. Include the genotype
where possible. b. Determine the probability that the couple’s first child will be affected.
Solution
Maternal Grandmother: Nt Maternal Grandfather: Nt Uncle: tt Mother: NX Father:
NN Woman: NX Husband's mother: Nt Husband's father: Nt Husband's Sister: tt Husband:
NX t = tay sachs X = unknown N = Normal gene There's a 50% chance the woman is a carrier
and a 66.6% chance the husband is a carrier. Going by what we know, there is a 1 in 12 chance
the child will have the disease. (24 total outcomes, only two result in the child having tay sachs)
