deoxycytidine, which is a methylated cytosine on the 5’ carbon of a cytosine, is involved in the process of cell differentiation and maintenance. Cell differentiation involves methylation of different areas within the DNA of a cell, which can alter the transcription of genes. During cell differentiation, DNA methylation is important for establishing the identity and function of a cell because of its role in controlling gene expression. A recent study looking at genome DNA methylation of newborn infants and humans aged 100 years or older found that the older individuals had significantly decreased overall DNA methylation. As one ages, the amount of DNA methylation slowly begins to decrease. Studies have also looked at methyl deoxycytidine residues from tissues collected from rodents at various ages. These studies found that DNA methylation loss increased significantly as the rodent aged. Thus, aging is related to a significant loss in DNA methylation. However, this loss of DNA methylation appears to be slowed by physical exercise under rare conditions, in general this effect is not very well studied and so far it seems like there is no connection between DNA methylation and physical activity. Further studies have looked at the effects of physical exercise on DNA methylation and aging in humans. Another component of aging is the gradual shortening of telomeres located at the end of chromosomes. Telomeres are repetitive sequences located at the end of chromosomes whose purpose are to slow the process of shortening and cell damage which occurs after every cell division as well as stabilize the ends of DNA. Aging and age-related diseases are associated with the significant shortening of these sequences. The shrinking of telomeres occurs in somatic cells where telomerase, the enzyme in control of telomere lengthening, is not expressed. However, it has been seen that telomeres can transcribe non-coding RNA, or functional RNAs that do not get translated into protein. Research has demonstrated that some of the non-coding RNAs transcribed at telomeres are involved in heterochromatin formation and stability of the telomeres. These non-coding RNAs can be positively impacted by physical exercise. Notably, a study found that mice exposed to short-term running phases had increased non-coding RNA transcription at telomeres as compared to sedentary controls. This increase in non-coding RNA transcription aided telomere stability, making the exercise group's telomeres less likely to be as affected by aging over time. Through helping to increase telomere stability, physical exercise can