Genetics, Vol 129, 925-930, Copyright © 1991


INVESTIGATIONS

Three-Locus Systems Impose Additional Constraints on Pairwise Disequilibria

W. P. Robinson, M. A. Asmussen and G. Thomson
Department of Integrative Biology, University of California, Berkeley, California 94720

Combinations of allele frequencies and pairwise linkage disequilibrium terms, each of which is permissible at the two-locus level, may not always be permissible at the three-locus level. These additional constraints on the possible maximum and minimum values for the pairwise disequilibrium terms are formally determined and numerically analyzed. In some cases, the three-locus constraints on a pairwise disequilibrium (D) may be equivalent to the usual two-locus constraints, while in others, the positive or negative range may be restricted. This can result in situations where the allowable values of D are limited to only positive or only negative values up to the extreme case where there is only a single admissible value. No additional restrictions are placed on pairwise disequilibrium values when four loci are considered, other than those imposed by the three-way combinations containing the two loci of interest. A new measure of normalized pairwise linkage disequilibrium, allowing for the three-locus constraints, is defined and illustrated by an application to data from the human histocompatibility antigen (HLA) system. An analogous normalized three-way disequilibrium measure is also formulated.


This article has been cited by other articles:


Home page
GeneticsHome page
M. N. Grote
A Covariance Structure Model for the Admixture of Binary Genetic Variation
Genetics, August 1, 2007; 176(4): 2405 - 2420.
[Abstract] [Full Text] [PDF]


Home page
GeneticsHome page
D. Meyer, R. M. Single, S. J. Mack, H. A. Erlich, and G. Thomson
Signatures of Demographic History and Natural Selection in the Human Major Histocompatibility Complex Loci
Genetics, August 1, 2006; 173(4): 2121 - 2142.
[Abstract] [Full Text] [PDF]


Home page
GeneticsHome page
K. L. Ayres and D. J. Balding
Measuring Gametic Disequilibrium From Multilocus Data
Genetics, January 1, 2001; 157(1): 413 - 423.
[Abstract] [Full Text]


Home page
GeneticsHome page
M. N. Grote, W. Klitz, and G. Thomson
Constrained Disequilibrium Values and Hitchhiking in a Three-Locus System
Genetics, November 1, 1998; 150(3): 1295 - 1307.
[Abstract] [Full Text]