They exist in all the cells of the body. They are inherited via sperm and egg cells.
They will not be inherited unless a similar damage has happened in eggs or sperms due to the same exposure to mutagen, In that case, progeny might show the mutation.
But they are an inherited mutation that was supported in fertilization of the egg during reproduction.
85% of adults are grandparents by age 65. This estimation has been made in the U.S. from the surveying of the elderly. So, the correct choice is the third option: 85.
