One of the causes of mammalian aging is the loss of epigenetic information . The expression levels of mRNA and protein endure significant changes as we age . Genes that exhibit age-dependent increases in mRNA and protein levels, along with increased cortical thickness during aging, link to sensory perception and immune function . Multiple changes in the copy number of many genes at the same time can lead to bad traits, such as defects that are caused by adding or removing certain genes . Additionally, large-scale changes in DNA copy number can lead to deleterious phenotypes.