Incomplete Pedigree Research Articles

Estimation of Variance of Maternal Lineage Effects Among Canadian Holsteins

Bayesian posterior estimates of variances of maternal lineage effects were obtained with a procedure that used Gibbs sampling. Data were records of yield during first parity from 245,510 Holstein cows that calved in Canada between 1990 and 1994. Maternal lineages were defined by tracing the maternal ancestry of cows to common female ancestors. Traits were standardized yields of milk, fat, and protein and percentages of fat and protein. Estimates of maternal lineage variance were <0.5% of the total variance for all traits. Effects of this size hardly affected the cow rankings for estimated breeding value. Another analysis defined maternal lineages by establishing groups of dams and their daughters in an attempt to maximize the variance of environmental effects associated with maternal lineages, but only 1.1% of the variance in milk yield was associated with effects of the dam and daughter groups. Analyses of simulated data indicated that positive estimates of maternal lineage effects were not a result of restriction of estimates to positive values and that estimates of maternal lineage variance were biased slightly downward because of incomplete pedigree information. The partitioning of maternal lineage and additive genetic variance was correct when pedigree information was complete, according to results from simulation.

Estimated inbreeding in a small, wild muskox Ovibos moschatus population and its possible effects on population reproduction

Knowledge of the effects of inbreeding in natural animal populations is limited. Although inbreeding depression is well documented in wild animals bred in captivity, it has been suggested that the phenomenon does not occur in nature. The potentially negative effects of inbreeding may be of great importance for the survival of small, wild populations. In a small free-living population of muskox Ovibos moschatus in Sweden, fecundity and longevity have decreased to the extent that the population now numbers only 12 individuals and is highly likely to die out in the near future. It is possible that this decline is due to harmful effects of inbreeding, the extent of which has been estimated using incomplete pedigree data in combination with computer simulations.

Cystic Fibrosis in Non-Caucasian Patients

The interpretation of a condition in genetically unusual circumstances is often handicapped by an atypical presentation, unusual course (variable penetrace?), or incomplete pedigree information, in addition to the constant hazard of unknown illegitimacy. For these reasons, the thorough study of two American Indian families with cystic fibrosis of the pancreas (Harris and Riley, Pediatrics, 41:733, 1968) is particularly valuable. The report prompted us to review the less satisfactorily documented non-caucasian patients with cystic fibrosis autopsied in the Johns Hopkins Hospital.