Kathryn T, (age 27) requested genetic counseling in order to receive presymptoma
ID: 80701 • Letter: K
Question
Kathryn T, (age 27) requested genetic counseling in order to receive presymptomatic testing for Huntington's disease. Kathryn's mother and maternal grandmother both died of the disease and her brother Thomas died 6 months ago from Huntington's at the age of 30. Kathryn has a living maternal uncle who is forty-five and affected by the disease and living maternal aunt who is fifty and apparently healthy. Kathryn feels she may have the gene and she has some finger and facial twitches. She is under the care of a neurologist and is receiving counseling for the possibility of Huntington's. Kathryn wishes to confirm if she is carrying the gene so she and her husband can make plans. In addition, she has a healthy, five-year-old daughter from an unplanned pregnancy. She is concerned her daughter may have inherited the gene. If Kathryn does not have the gene, then she and her husband would like to have more children. Specimens from blood banked by her deceased brother, her affected uncle and Kathryn were tested and the results indicate that in all probability, Kathryn has the gene for Huntington's disease. Noncarrier female Carrier (heterozygous female) Possible carrier female Normal male Affected male Use the symbols the right to and develop a pedigree for inheritance of Huntington's disease in Kathryn's family. What is the probability that Kathryn passed this gene to Lindsey? a. If Kathryn has Huntington's b. If Kathryn does NOT have Huntington's What would you infer about the genotypes of Kathryn's maternal great-grandparents?Explanation / Answer
a) If karythan has disease it means that she will have two affected allels (A0A0) but her husband (AA).so the child is not going to have disease.she might be a carrier(A0A).she can have disease only in one condition - if karythan husband either be a carrier or affected.so there is zero probability if her karythan is affacted but her husband is nromal.
b) if she is normal than her daughter will be normal.than there is zero probability.
The genotype of her maternal great grand parents could be: both could be carrier(AA0 ) or both would be affected A0A0 then only there was the possibility of her grandmother having the disease.
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