Board Thread:Character Discussion/@comment-28282242-20160423112213/@comment-27404483-20170505224832

It's not really a gene as it is a genetic mutation. A gene would mean it needs to be passed down, but if "To be Heda is to be alone" A commander probably hasn't had children in order to pass down the gene.

To become commander the nightbloods battle to the death at usually young ages, so no existing nightbloods have children, meaning the gene should have died by now. A mutation, however, would stick around if Becca had injected a lot of grounders, which she may have she had an entire suitecase with the syrum so it's not too off to assume she gathered her own army and injected everyone with the stuff to make as many nightbloods as possible.