(genetics) The process by which a small population accumulates harmful mutations, which leads to loss of fitness and decline of the population size, which may lead to further accumulation of deleterious mutations due to fixation by genetic drift.

Tumour mutational burden (abbreviated as TMB) is a genetic characteristic of tumorous tissue that can be informative to cancer research and treatment.

characteristic combinations of mutation types arising from specific mutagenesis processes such as DNA replication infidelity, exogenous and endogenous genotoxin exposures, defective DNA repair pathways, and DNA enzymatic editing.