Originally Posted by NamikazeNaruto
I don't think it would be weaker, but a highly recessive trait. It would probably evolve and possibly the same qualitys. Meh, im not going to theorize on this as we have no manga evidence but Senju had to have mixed with other clans in the village.
I said weaker because It seems that Neji and Hinata's father seemed to have strong genes, especially coming from the head of the branch family. Sasuke and Itachi seemed have had stronger Uchiha chkara kinda like Madara and his brother, and the 1st and 2nd Hokage seemed to have stood out in their clan. Since all Senju, Uchiha and Hyuuga likely all started out from 2 different men who both got their gifts from 1 guy, im assuming that the strongest of their genes were kept that strong in those individual families because they had the "purest" of that kekke genkai dna, meaning less outside blood mixed in it compared to their other clansmen. And out of all the Senju blood that must be somewhere in Konoha, nobody but Naruto and Jiraiya seem to stand out when it comes to natural stamina. Still its only, just my assumption/guess which holds no water really.
It probably would just be a more recessive gene and not necessarily a weaker Sharingan with weaker chakra. I agree that Senju possibly did mix with other clans in the village and either those offspring stopped being shinobi, took their non Senju father's last name, or they changed their last name like Senju and Uchiha changed theirs from whatever it was before they decided to single themselves out from the family that they were. They all started as 1 clan with 1 last name I presume, which would have been the last name of the 1st Sage.