nongenetic

Nongenetic is an adjective used in biology to describe phenomena, processes, or information transmission that affect organisms and their descendants without changes to the DNA sequence.

Definition and scope: In biology, nongenetic refers to heritable information conveyed across generations that does not arise from changes in the DNA sequence. This includes epigenetic inheritance, cytoplasmic inheritance, and transmission mediated by symbionts or protein conformations.

Mechanisms: Epigenetic modifications such as DNA methylation, histone modifications and non-coding RNAs can influence gene expression in offspring; some marks are reset during development but can persist for a generation or more in some lineages. Imprinting is a specific form of parent-of-origin epigenetic inheritance. Cytoplasmic inheritance includes organelles with their own genomes (mitochondria and chloroplasts) transmitted through the egg, and maternal effects where the phenotype of offspring is affected by the mother's state. Microbiome transmission, such as vertically transmitted bacteria, also constitutes nongenetic inheritance. Prions are misfolded proteins capable of transmitting phenotypic states without nucleic acids, observed in yeast and some animals.

Significance and debate: Nongenetic inheritance can influence evolution by introducing heritable variation independent of DNA sequence; its stability across generations varies by mechanism and organism, and it is subject to ongoing debate about its prevalence and adaptive significance. Epigenetic marks can be reset during germ cell development, limiting persistence. Prions and some cytoplasmic factors can persist longer. The distinction between environmental influence and inherited information can be nuanced.