Preferential transmission of the Z deficient allele of alpha 1-antitrypsin

The transmission of the Z deficient allele of alpha 1-antitrypsin was studied in 23 families, each with a single parent heterozygous for this allele. When the mother carried the Z allele, the distribution of phenotypes in the children did not differ significantly from the expected frequency. In contrast, when the father was the carrier, a significant increase of heterozygous phenotypes was observed in the children. This observation suggests that a selective advantage is associated with the expression of the Z allele in male gametes.