Grey Templar wrote:actually, a Mature Marine can have one of his progenoids extracted. the other will begin to replace the lost progenoid.

Progenoids can also be multiplied inside a host human who has been genetically engeneered to do this. 1 will split into 2.


the process is long and slow, but over time a few marines can make many more.


nowhere does it say this exactly in the fluff, but if you read Codex SM very carefully in the implant section you will notice it says a Mature Progenoid can be extracted and used to make more marines and so a chapter relies on its marines to make more, it doesn't say it has to involve the death of a marine. indeed, relying on a marine to make a marine wouldn't make any sense if it had to involve the death of one.

many chapters have lost the live extraction tecnique, but Geneseed can be replicated outside of the Marines body. Chapters are required to send Geneseed samples to Terra every so often to check for Genetic purity.


so to answer your original question. a marine could get another set of genes placed inside, but they wouldn't because 1) his other progenoid would replace the lost one, and 2) a different set of genes(each is similer, but not identical) could cause problems.