The hayflick limit isn't the only cause of senescence. There are many biochemical processes that can induce senescence, and a variety of reasons the cell might

The hayflick limit isn't the only cause of senescence. There are many biochemical processes that can induce senescence, and a variety of reasons the cell might do that. Oncogenic stress from reactive oxygen species, double stranded DNA breaks, enzymes like p53 tumor suppressor (this is a big one) and histone deacetylase inhibitors can all lead to senescence. Also, the hayflick limit has little to do with DNA damage per se, but rather is about telomere shortening. DNA is replicated in a ssomewhat asymmetrical fashion, and at the end of the chromosome, and needs the telomere to act as a buffer. Eventually you run out of buffer because every replication loses a little bit. But there's no innate damage to the DNA related to telomere shortening - all of the generic code still is maintained. >Btw: are organelles just protein complexes? If so organelles are made by DNA too. No... Not even close. There are some proteins in them and proteins interact with them but organelles are extremely complex. They are structures made of lipids, proteins, minerals, RNA, etc.