Effects of P element insertions on quantitative traits in Drosophila melanogaster.

TLDR

P element mutagenesis generated 94 third‑chromosome Drosophila lines with an average of 3.1 stable insertions, and the homozygous and heterozygous effects on viability and bristle number were evaluated by comparison to insert‑free controls. Each P element insertion lowered homozygous viability by 12.2 % and heterozygous viability by 5.5 %, induced recessive lethal mutations at 3.8 % per insert, and contributed modest but sex‑dependent mutational variance to bristle number, with large, largely recessive effects skewed toward bristle loss and few lines driving most of the variance while also reducing viability.

Abstract

Abstract P element mutagenesis was used to construct 94 third chromosome lines of Drosophila melanogaster which contained on average 3.1 stable P element inserts, in an inbred host strain background previously free of P elements. The homozygous and heterozygous effects of the inserts on viability and abdominal and sternopleural bristle number were ascertained by comparing the chromosome lines with inserts to insert-free control lines of the inbred host strain. P elements reduced average homozygous viability by 12.2% per insert and average heterozygous viability by 5.5% per insert, and induced recessive lethal mutations at a rate of 3.8% per insert. Mutational variation for the bristle traits averaged over both sexes was 0.03Ve per homozygous P insert and 0.003Ve per heterozygous P insert, where Ve is the environmental variance. Mutational variation was greater for the sexes considered separately because inserts had large pleiotropic effects on sex dimorphism of bristle characters. The distributions of homozygous effects of inserts on the bristle traits were asymmetrical, with the largest effects in the direction of reducing bristle number; and highly leptokurtic, with most of the increase in variance contributed by a few lines with large effects. The inserts had partially recessive effects on the bristle traits. Insert lines with extreme bristle effects had on average greatly reduced viability.