00:03
So e .kl .i have a single circular chromosome.
00:09
So if you grow e.
00:10
Coli in the presence of radioactively labeled nucleotide, these will be incorporated into their chromosome dna during dna synthetists.
00:22
Say that you perform a post -chase experiment in which you grow bacteria in the presence of radioactive nucleotide.
00:30
Then imagine that you were able to completely remove the radioactive nucleotide.
00:34
From the medium immediately and then grow the bacteria exactly for two rounds of dna and cell division.
00:42
So what portion of the bacteria at the end of these two cell division would be radioactive chromosome on dna? why? so let's say this is the chromosome of bacteria.
00:53
I'll draw right here.
00:55
It's circular and it has two copies because dna is double -stranding structure.
01:02
And i used red to show the radioactive label.
01:06
Now, after it grow in a radioactive labeled medium, both strands of dna obviously will be made up of radioactive nucleotides.
01:16
So now you remove the radioactive nucleotides and grow them into non -radioactive medium.
01:23
So after the first round of, i guess, cell dna replication, as you can see, adopt a semi -conservative model.
01:37
So what is semi -conservative? so that means one copy of the dna will be used as a template, and the other copy will be new by using a new nucleotide.
01:53
So as you can see, according to a semi -conservative model, the two strands of the chromosome dna will separate.
01:59
So you have a red circle, which is radioactive labeled, then the new strand of dna will be made up of non -radiolactive nucleotides, which is i'm going to use black.
02:13
So the black one is non -radiolactive label...