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Do bilineal pedigrees represent a problem for linkage analysis? Basic principles and simulation results for
1Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, New York.
Genetic Epidemiology
|January 1, 1992
Summary
Bilineal pedigrees can be included in genetic linkage studies for single-gene disorders. While they may offer slightly less information than unilineal families, the loss is often minimal and does not warrant automatic exclusion.
Area of Science:
- Genetics
- Statistical genetics
Background:
- Concerns exist regarding the utility of bilineal pedigrees in genetic linkage studies, particularly for psychiatric disorders.
- The informativeness of bilineal versus unilineal families for genetic linkage analysis requires careful evaluation.
Purpose of the Study:
- To compare the informativeness of bilineal and unilineal families for linkage studies of homogeneous single-gene disorders.
- To quantify potential information loss in bilineal pedigrees and identify contributing factors.
Main Methods:
- Simulation studies using three-generation pedigrees to compare bilineal and unilineal datasets.
- Calculation of expected lod scores (ELODs) in nuclear families.
- Calculation of Fisher's information number I(theta) in nuclear families.
Main Results:
- Extremely bilineal datasets showed a ~50% drop in mean maximum lod score compared to purely unilineal datasets.
- Less extreme bilineal datasets, more representative of real data, exhibited minimal lod score drops (<10% or near zero).
- Information loss in bilineal families was greater for phase-unknown matings than for phase-known matings.
Conclusions:
- Bilineal families are not so uninformative as to be automatically excluded from linkage datasets for homogeneous single-gene disorders.
- The degree of information loss depends on pedigree structure, genetic model, and marker informativeness.
- The study discusses implications for linkage studies involving heterogeneous disorders.