Meselson and Stahl DNA experiment help

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hihellohowareyou
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Meselson and Stahl DNA experiment help

Post by hihellohowareyou » Mon May 02, 2011 9:14 pm

I am answering questions for an online lab and I have no clue what is going on. Here are two pictures of what is going on in the lab.
Image
Image

Which model(s), if any, is ruled out by the experimental results of replication cycle 1? Explain.

Which model is proved correct by the experimental results of replication cycle 2? Explain.


The only thing I know is that the semiconservative model is what is correct, I just don't know how to come to that conclusion based on the experiment. Any help is appreciated! Thankyouu.

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JackBean
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Post by JackBean » Mon May 02, 2011 9:39 pm

Well, the original molecules were full of 14N, while the new nitrogen was 15N.
In first step you get only one band, thus all molecules must weight approx. the same. Which theory contradicts that?
In the second step, after you added 14N again, you get 2 bands. One of them is the same as in WT. How is that?
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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JackBean
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Post by JackBean » Mon May 02, 2011 9:39 pm

Maybe try to picture, what would happen in both steps, if either hypothesis was correct ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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