I think tails are a recessive trait when it comes to half-saiyans. (still not sure about quarter saiyans like Pan, but it could possibly be the same situation with them as well) Bulla was obviously not born with a tail, as the viewers saw her birth. In following episodes after her birth in Super, she is never seen with a tail. Trunks didn't have a tail in DBZ when he was a baby either, and same with Goten too. Gohan must've gotten lucky with his tail, as he's the only half-saiyan on Earth with a tail. We know as a fact that pure-blooded saiyans (from Universe 7 that is) are always born with tails, so that biology must get a bit messed up when a saiyan has a child with a human. Also, I'm pretty sure that the lesser amount of saiyan blood that someone has in their body, the least likely they are to have a tail. Goku Jr. and Vegeta Jr. were not seen with a tail, and they are 1/16 saiyan. Pan was not seen with a tail either, and she's 1/4 saiyan. It must be more common with half saiyans, but of course, since tails are a recessive trait, that doesn't mean all half-saiyans will have tails. That's really all I can think of, I don't see any other reason why Trunks, Goten, and the others don't have a tail.
I already explained that just simple recessive inheritance wouldn't work here, because all of the half-Saiyan children have the same genotype, so either all of them have tails or don't. If we take the tail locus as "T-t", where "T" means they have no tail and "t" means they have a tail. Goku and Vegeta would have the genotype "tt" since he had a tail, while Chi-Chi and Bulma have "TT" for no tail. All of the first generation half-Saiyan children would have "Tt" since they are halfbreeds.
The recessive thing only works if two hybrid parents (both "Tt") have children. So that 1 in 4 of their children would possess the "tt" genotype.
BH Ouji wrote:
And why would he done that?
Do you thought Arabic dub of DBZ is canon and Gohan thought "Oh man better cut my dear younger brother's tail, or else he will summon his Oozaru"
I read it somewhere. And yes, of course it would have been to prevent the Oozaru thing.