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Current time:0:00Total duration:2:12

Semi conservative replication

AP.BIO:
IST‑1 (EU)
,
IST‑1.M (LO)
,
IST‑1.M.1 (EK)

Video transcript

let's take a piece of DNA and let's just unwind it into its two strands and just help us remember that DNA is really a very very long molecule I'm going to put arrows here on our two strands of DNA and the question I want to ask you is if we were to replicate this DNA what would the end result look like so I'm kind of skipping over the entire process of how the DNA is replicated and focusing just on the product and so we have three choices the first is conservative replication and in conservative replication we have our old pair of DNA and then we synthesize a completely new pair of DNA so you can see the old pair that looks just the same as what we had before and yellow and then we have a completely new pair which is represented in blue our next choice is dispersive replication and in dispersive replication we're going to end up with two pairs of DNA and in each one of those pairs we have some old DNA and new DNA dispersed within that double stranded DNA so you can see there's yellow and blue mixed up together and it wouldn't necessarily have to be in the ratio that I drew it in I drew it in this kind of neat ratio where the yellow and blues are the same size but perhaps the yellows would be a little bit bigger and maybe some of the blue parts smaller or vice versa and the third option we have is semiconservative replication and in semiconservative replication each pair has one old strand that you see in yellow of course and one new strand that's in blue and this question was answered by two scientists one by the name of meselson and one by the name of Stahl and they conducted a famous experiment which was named after them so the nasal sin stall experiment and in this experiment they proved that DNA replication is semiconservative so this is how DNA is replicated