system
Given the following post, respond as if you're commenting on Reddit:
human
Would a 70 year old brain transferred into into an 18 year old clone body,still die of old age? Also what is the biggest obstacle to performing this procedure?
gpt
First, the clone would die of old age. Our DNA has telomeres at the end of it, and every time your DNA is copied for a new cell, these telomeres shorten, which is theorized to be somehow related to aging (the idea is that one these telomeres get too short, they can no longer work as protective caps on the DNA so it won't copy anymore and that cell has effectively died). Since a clone comes from a cell from the 52 year old body, in 18 years though the clone body will be 18, the cells will have telomeres the length of a 70 year old's.

With the brain itself, this problem likely wouldn't be quite as dramatic, because neurons divide much more slowly than the rest of the body, and so the brain's cells probably aren't physically nearly as old as any other cells in the body. If you could indeed transplant a brain, it may be able to outlast many bodies (robot bodies, anyone?).

Though the brain is covered by an outer layer that is connected to the inside of the skull at a few points to keep it from sloshing around too much, the biggest obstacle to moving it from body to body would be the spinal cord. With today's technology, it is impossible to reconnect that many nerves accurately, not to mention that the surgery would take so long that the brain would die- it wouldn't be a surgery like a heart transplant. We can reconnect things like the tips of fingers and have decent success in attaching enough nerves and muscles and blood vessels to allow it to work, but we aren't advanced enough for brains.