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Please answer in simple terms im only in 9th grade.

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closed as off-topic by Atl LED, kmm Feb 2 '14 at 21:22

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework questions are off-topic on Biology unless you have shown your attempt at an answer. For more information, see our homework policy." – Atl LED, kmm
If this question can be reworded to fit the rules in the help center, please edit the question.

up vote 2 down vote accepted

Hershey and Chase did two experiments to prove that DNA is the carrier of the genetic information. First, they grew phages (viruses which infect bacteria) in a medium containing radioactive sulphur (35S). This marked all the proteins of the phage (the hull) radioactive. They then used this phage to infect bacteria. To do so, the phage attaches to the surface of the bacteria and injects its genetic material. This looks like in this picture from the Wikipedia page on Bacteriophages:

enter image description here

The bacteria with the attached phages are then blended, so they will loose the attachment to the bacterial surface. The mixture of bacteria and phages is then centrifuged, this makes the heavy bacteria sediment at the bottom of the tube, the lighter phages stay in the supernatant. Hershey and Chase then measured where the radioactivity from the marked phage proteins had gone, since they found it in the supernatant, they knew, that no proteins had entered the bacteria. If proteins would have been the carrier of the genetic information they would have entered the bacteria and had been found in the sediment inside the bacteria.

In the second experiment (the proof if you want to say so) they marked the DNA of the phages radioactive (with radioactive phosphorus, 32P). They repeated the experiment and found the radioactivity in the sediment with the bacteria, proving, that the DNA had indeed entered the bacteria. If the DNA wouldn't be the carrier, it wouldn't have entered the bacteria and would have stayed in solution.

The whole experiment is nicely shown in this Wikipedia illustration:

enter image description here

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this was very good thank you:) – jack Feb 2 '14 at 20:40

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