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Segregation analysis and genetic counseling when both parents carry balanced chromosomal translocations
O P Phillips1, A T Tharapel, L P Shulman
1University of Tennessee, Memphis.
Objective:
To assess the risk of chromosomally abnormal offspring and discuss counseling approach when both parents carry balanced translocations.
Design:
Theoretical segregation analysis is performed and use of empiric data is used in genetic counseling.
Setting:
Patients are referred to Division of Reproductive Genetics at the University of Tennessee, Memphis.
Patients, Participants:
The mother, heterozygous for reciprocal translocation 46,XX, rcp(7;13)(p21;q22) and father, heterozygous for Robertsonian translocation 45,XY,rob(13q;14q) were referred for genetic counseling concerning risks of chromosomally abnormal offspring.
Interventions:
Segregation analysis, genetic counseling, and chorionic villus sampling.
Main Outcome Measure(S):
A cumulative risk was derived to use for counseling purposes. Cytogenetics using GTG-banding was performed on cultured chorionic villus cells.
Results:
Theoretical risk of this couple having chromosomally abnormal offspring was 40.5%. On the basis of empirical data and risk factors inherent in the specific translocations, the maternal contribution at midtrimester was 3.5%; the paternal contribution was 1% to 2%. The sum of these risks was used in counseling.
Conclusions:
The fetus was found to be 46,XY,rcp(7;13)(p21;q22).