Sex, gender, and epigenetics of aging and longevity

Term epigenetics encompasses heritable modifications not stemming from changes in DNA sequence. These modifications influence the individual phenotype by regulating gene expression and activity. Specifically, DNA methylation and histone modification, involving covalent and noncovalent changes to DNA and histone proteins, respectively, modify DNA accessibility and the whole chromatin structure, thereby governing gene expression patterns. More recently, the field of epigenetics has expanded to include the role of small noncoding RNAs in shaping gene expression levels. Since these processes are influenced by environmental factors, epigenetics is often viewed as a link between the genome and the environment in defining aging and longevity phenotypes. Males and females exhibit sex-specific expression in a wide range of genes, including metabolic enzymes, which affect both basic physiology and the response to environmental exposures.