Epigenetic Contribution to Covariance Between Relatives

Epigenetic inheritance is a physical variation from generation to generation from influences other than DNA. Epigenetic inheritance occurs between asexual and sexually reproducing organisms, and directly affects the hereditary structures of populations, which can potentially lead to evolution. Research has pointed to considerable epigenetic inheritance from generation to generation. This research can be used to evaluate the risk for disease and responses to environmental stresses in a population. They introduced a model that takes both the probability of passing on ancestral phenotypes and stimulations from the environment. By doing this they are able to show changes between relatives. They were able to identify physical characteristics and populations where epigenetic inheritance had occurred.

To make this model they looked at heritable epigenetic variability, which is a physical characteristic that is brought upon by the environment or inherited by previous generations. The also looked at the reset coefficient which refers to the probability of a generation changing its epigenetic state, so that it can respond to its current environment with no memory of the past. The last thing they looked at was coefficient of epigenetic transmissibility, which is the probability of passing on the epigenetic changes to the next generation, without reset. These apply to both asexually and sexually reproducing organisms.

They looked at a continuous trait with genetic, epigenetic, and environmental variability. They simulated environmental exposure to organisms by way of heat shock or chemicals. After doing this two questions arose: “Can we distinguish between heritable epigenetic and genetic inheritance?” and “How can we estimate the epigenetic transmissibility?” To answer this they compared covariance between relatives. They measured the covariance between parents and offspring, between sibs, and between uncles and nephews. To examine asymmetric (parent is not identical to its offspring) and symmetrical (parent cell is also the offspring cell) they followed single cells over multiple generations. They found that during sexual reproduction, the reset mechanism is more noticeable than in asexual reproduction.

Transgenerational, ecological or developmentally induced physical characteristic changes have been mainly studied with maternal effects and are looked at as temporary effects. While cultural transmission was just studied as the complex system of cultural practices. Thus these studies have only started in recent years. Without detailed molecular studies, it is very difficult to detect epigenetic inheritance, since deviations from classical Mendelian ratios can be always explained by assuming interactions with modifier genes. In asexually reproducing, multicellular organisms, rapid and heritable physical characteristic switches are usually explained within the support of somatic mutations and somatic selection or various types of phase variations.

This research is interesting to see how our environment and lifestyles can change us and effect our future generations. It shows us that not all diseases and mutation are brought upon by genes, but rather by our environment and the environment or our past generations. We have an astounding effect on our bodies and if we are not careful and take care of it, we can bring drastic and dangerous effects to our future generations and ourselves.

~Kevin Reynolds