And likewise, when these two separate and when we use this purple N 15 band, what happens is we essentially form this molecule here. But when these two separate and instead we use the brown strand here and the brown strand here because we have the N 14 in our mixture and the N 14 will be used to synthesize that. Dodostran these are the DNA molecules that we're going to form and they're going to consist purely of these N 14 atoms. And because N 14 is lighter and less dense than the N 15 this will be this band right here. So this is purely N 14 while this band here is the N 14 N 15 because it consists of a combination. And likewise this band describes the N 14 and 15 DNA molecule in which half of it is that original parent strand and the other half is that newly synthesized N 14 lida strand.