Senescence, cancer, and immortality

Abstract

The definition of senescence is the scientific term for biological ageing; the definition of which is the change in the biology of an organism once it has reached maturity. Senescence progresses through cell divisions and in order for DNA in a chromosome to remain undamaged, it needs telomeres as shown by the white caps in Figure 1. A telomere is DNA that does not code for anything, but is merely ‘a repetitive nucleotide sequence’, and this prevents the damage that would otherwise happen to the chromosome.[1] During cell division, when DNA is being replicated, Okazaki fragments (strands of RNA containing 1,000-2,000 nucleotides) need to be connected together to form DNA after the last RNA primer has attached. Unfortunately, in order for the Okazaki fragments to connect together, bits of the RNA need to be cut off.[2] Therefore, over time, telomeres or, meaningless DNA that codes for nothing, have evolved so as to prevent useful DNA from being left out. These telomeres have the code TTAGGG repeated many times.[3] However, over time the number of telomeres in the body decreases. Humans begin with around 7,000-10,000 nucleotides worth of telomeres, Alex Joseph