A new open access study highlights that epigenetic changes can persist through many generations. While the researched worked with plants, the situation is surely very much the same with animals and humans.
F. Johannes et al., Assessing the Impact of Transgenerational Epigenetic Variation on Complex Traits. PLoS Genetics, 2009.
Loss or gain of DNA methylation can affect gene expression and is sometimes transmitted across generations. Such epigenetic alterations are thus a possible source of heritable phenotypic variation in the absence of DNA sequence change. However, attempts to assess the prevalence of stable epigenetic variation in natural and experimental populations and to quantify its impact on complex traits have been hampered by the confounding effects of DNA sequence polymorphisms. To overcome this problem as much as possible, two parents with little DNA sequence differences, but contrasting DNA methylation profiles, were used to derive a panel of epigenetic Recombinant Inbred Lines (epiRILs) in the reference plant Arabidopsis thaliana. The epiRILs showed variation and high heritability for flowering time and plant height (~30%), as well as stable inheritance of multiple parental DNA methylation variants (epialleles) over at least eight generations. These findings provide a first rationale to identify epiallelic variants that contribute to heritable variation in complex traits using linkage or association studies. More generally, the demonstration that numerous epialleles across the genome can be stable over many generations in the absence of selection or extensive DNA sequence variation highlights the need to integrate epigenetic information into population genetics studies.
Not all is hardcoded in the genome, the program can be and is in fact altered by "softer" means, means that have nevertheless certain transgenerational persistence. This way the phenotype is changed without need for the genome to mutate. Non-genetic variants appear around a basic genic core, increasing variability and potentially adaptability in the short run too.