system
Given the following post, respond as if you're commenting on Reddit:
human
Could DNA have a form of primitive "password protection"?

This question is inspired by a recent post about Covid RNA and why it had a polyA tail (a long sequence of As) at the end. The answers explained that this was a way of tracking the health of the RNA and that it was required for the proteins to be expressed.

Could an organism create a unique or semi unique tail (rather than simply a long series of As), a sort of "password", and use that as a form of protection against viruses that would need to know the exact "password" to hijack the specific organism?
gpt
Bacteria do this! But not exactly in the way you are describing. One protective mechanism that bacteria use to avoid unwanted genetic material (e.g. phages) from hijacking them is to protect their genomes using methylation. The bacteria typically have an enzyme that adds methylation to a certain sequence and a corresponding restriction enzyme that chews up any DNA that isn’t protected by said methylation.

As an aside, that discovery was foundational to molecular biology, all from someone looking into how bacteria defend themselves from pathogens.