Epigenetics: We are not just the product of our genes.
Life before birth explains how the environment in which we develop in the uterus alters our appearance and our life-course health. See Chapter 4 Life Before Birth.
Genetically identical agouti mice often have very different coat colors. Increasing the amount of folate in the mother’s diet darkens the coat color of her offspring. Rob Waterland and Randy Jirtle showed that this occurs by increasing the amount of methylation of the agouti gene, permanently darkening the color of the offspring’s hair. The coloring is variable among the fetuses within the litter because the amount of folate crossing the placenta to each fetus will differ depending on that particular fetus’ placental blood flow and function This study showed, for the first time, that a transient nutritional exposure during a critical period of development can cause an epigenetic change that leads to a permanent change in an animal’s body characteristics. So, it is clear that epigenetic factors will determine our final structure and function. Figure kindly provided by Robert Waterland.
Waterland RA, Jirtle RL. Transposable Elements: Targets for Early Nutritional Effects on Epigenetic Gene Regulation. Mol Cell Biol [Internet} 2003 Aug 1; 23(15):5290-300. Available from: https://pubmed.ncbi.nlm.nih.gov/12861015/