Download Prenotes

Bio A Prenotes - Molecular
SCIENCE AT WORK How do we prove that the hereditary material is DNA?
1. Griffith – Does a material exist that we can prove transfers “characteristics”?
a. Used two types of bacteria. One causes a deadly disease (smooth) and one does not
i. But if the deadly one is killed (by heat), it appears that something inside the
dangerous bacteria can be transferred to the “non-dangerous” bacteria.
b. Griffith has discovered a molecule that can be transferred and carries “characteristics”
with it. He names this _____________________________________
2. Avery/ McCleod – Can we show that the transforming material is DNA?
a. Similar experiment to Griffith’s BUT….
i. First treated cells with enzymes that digest protein, carbs, RNA and lipids
bacteria were still transformed
ii. BUT if cells are treated first with enzymes that digest DNA  no
transformation!!!
b. What does digesting a molecule do?
c. What did this experiment show?
3. Hershey/Chase – A better experiment to show the transforming material is DNA?
a. Similar to Avery/McCleod but used a better model system
i. Bacteriophage has ONLY protein and DNA (not all the other molecules).
ii. Much better for “being sure”
iii. Used radioactive S (which becomes a part of the virus coat) OR radioactive P
(which becomes a part of the DNA) to create the viruses.
b. When the viral DNA is radioactive, does the cell become radioactive?
c. IF we make the protein coat of the virus radioactive, does the cell become radioactive
c. If the virus causes diseases, would the protein or the DNA result in creating the same
disease in the bacteria?
Bio A Prenotes - Molecular
Determining the structure of DNA.
1. Done with many scientists, but predominantly Franklin (and Wilkins) AND Watson and Crick
a. The X-ray diffraction (pattern of the bases) was shown through X-ray diffraction (F
and W). BUT…Watson and Crick put it all together to make the
3D model!