00:01
Mesocyn and starr used heavy nitrogen as the 15th to test the prevailing model of dna replication.
00:08
They allowed bacteria with n15 labeled dna to replicate their dna twice in a medium containing exclusively n14, which is the light nitrogen.
00:19
Then used equilibrium density gradient centrifugation on dna extracted after the first and second replication cycle.
00:27
Now, if dna replication was conservative, what would be expected for the first replication cycle? so now let's assume that it's conservative instead of the actual semi -conservative.
00:42
In conservative model, basically the two old strands stay together and the two new strands are together.
00:56
So as you can see, the question is asking about the dna replication for the first replication cycle.
01:12
So you start out with n15 and then you move that exclusively into n14 medium.
01:21
Now after the, this is generation zero, this is after one cycle, you can see according to conservative model, you have two old dna stay together.
01:32
So this is n15.
01:33
And then you have made a new strand, which are made of purely new dna, which were made of n14 only...
