Board Thread:Naruto Discussions/@comment-26431570-20190526171926/@comment-25632268-20190527090726

RikudoKatsudon wrote: But that doesn't explain why Tsunade, a descendant of Mito's, has no whiskers. So any guess is as good as mine.

If I remember correctly, Hashirama and Mito got married before Madara left the village, so it is possible Mito was a mother before becoming jinchuuriki. That would explain why Tsunade has no whiskers despite being related to Mito.

But again, Kishimoto never really cared about it.