The Lansing effect and age-mediated changes in genetic parameters

Abstract

The influence of variation in age of grandparents upon the heritability of two metric characters has been studied in the guppy (Poecilia reticulata) and Drosophila melanogaster. In both cases effects on heritability paralleling those already demonstrated to occur with variation in parental age were found and may be regarded as examples of Lansing effects.Analysis of components of variance of sternopleural bristle number in Drosophila suggest that the genotypic variance for this character is increased in the progenies of older parents, largely as a consequence of an increase in additive genetic variance. It appears probable that this results from age mediated changes in mechanisms of gene control.Both the effects described seem likely to be reflections of fundamental aspects of ageing processes in biological systems.

Parental age dependent changes as a source of genetic variation in Drosophila melanogaster

“…Medawar, 1952;Williams, 1957;Szillard, 1959;Orgel, 1963;Comfort, 1964;Curtis, 1966;Sinex, 1974;Kirkwood, 1977;Sacher & Hart, 1978;Kirkwood & Holliday, 1979). Beardmore and Shami (1985) found that the genotypic variance for sternopleural bristle number in Drosophila had increased in the progenies of older parents, largely as a consequence of an increase in additive genetic variance. Beardmore et al (1975) showed earlier that the heritability of previously mentioned quantitative traits increases with advance in parental age, which had been also demonstrated in other metric characters, such as caudal fin ray number in the guppy fish (Beardmore & Shami, 1976), as well as in a twin study of total finger ridge count in man (Lints, 1978).…”

Epigenetic inheritance and aging

“…44 An effect of parental age on traits in the offspring has been found for skeletal characters in mice, 45 for egg size, bristle number, wing size, development time and other characters in Drosophila, 46 for the number of generations of asexual progeny in the protozoan Paramecium, 16 and for the heritability of some traits in fish, 47 Drosophila 48 and man. 49 The incidence of many human hereditary traits depends on the age of the parents.…”

“…Earlier, Beardmore and Shami suggested that inherited chromatin changes could be responsible for the changes with increasing parental and grandparental age in the heritability of various metric characters in the guppy and in Drosophila. 47 Although at present it is difficult to know whether particular parental-age effects are the result of genetic, epigenetic, or environmental factors, there is one category, Lansing effects, that seems particularly likely to have an epigenetic basis. Lansing effects are parental age effects that are transmissible, cumulative and reversible.…”

Lamarckism and Ageing

“…A puzzling set of observations is that the heritahiliiy of some traits also increases with age; this has been found for the number of caudal fin rays in the fish Poecilia reticulata [39], for sternopleural bristle number in Dro sophila [39,40], and for finger ridge counts in man [41], With most characters, the vari ation which depends on parental age is at tributable more to maternal than to paternal age, but the age of the father can certainly affect some characters in the offspring [33,38],…”

“…However, Beardmore and Shami [39] tenta tively suggested that chromatin changes causing alterations in gene expression may have been responsible for the increased heritability of metric characters which they found with increasing parental and grandparental age in Drosophila and P. reticulata. We believe that there are indeed several fea tures in their data and that from other stud ies of parental age effects and Lansing ef fects which support an interpretation based on epigenetic inheritance.…”