DNA History Webquest Name ______________________________________
Using the links provided, work your way through the history of the discovery of DNA as genetic material..
1. Friedrich (Fritz) Miescher ( http://www.dnai.org/timeline/index.html )
Find Miescher on the timeline and click on the bucket with the Red Cross to watch the animation. In 1869, he extracted a substance from white blood cells that he called nuclein. What do you think he was actually extracting?
2. Frederick Griffith ( http://library.thinkquest.org/20830/Textbook/HistoryofDNAResearch.htm )
or (http://biology.clc.uc.edu/courses/Bio104/dna.htm ) Frederick Griffith’s famous experiment was conducted in 1928.
What happened when smooth (S) virulent bacteria were injected into mice? __________________
What happened when the rough (R) bacteria were injected into mice? _______________________
What happened when heat-killed (S) bacteria were injected into mice? _______________________
What happened when heat-killed S and normal R bacteria were mixed and then injected into mice?
________________________________________________________________________________________________.
In his experiment, ______________ bacteria plus ______________ bacteria killed mice. Something was transferred into the Type R bacteria; all that the Type S bacteria could have transferred was DNA. His experiment demonstrated that DNA was the _______________ material.
3. Alfred Hershey and Martha Chase ( http://biology.clc.uc.edu/courses/Bio104/dna.htm )
What is a bacteriophage?
How does a bacteriophage kill a bacteria?
Which radioactive materials did Hershey and Chase use in their experiment? Explain why these radioactive materials were used.
In 1952, their experiments showed that ________ is the genetic material instead of _______________.
4. Erwin Chargaff ( http://www.dnai.org/timeline/index.html )
Watch “Chargaff’s Ratios.” Chargaff used relative proportions of bases in DNA to come up with his rules for base pairing.
What are 4 sources of DNA that he used?
http://fig.cox.miami.edu/~cmallery/150/gene/chargaff.htm
Adenine (A) pairs with ___________________ and Guanine (G) pairs with ______________________
The bases that are purines are __________________ and ___________________. They have ___________ carbon-nitrogen rings.
The bases that are pyrimidines are _______________ and ____________________. They have _______________ carbon-nitrogen rings.
5. Rosalind Franklin ( http://www.dnai.org/timeline/index.html )
Click on Rosalind’s picture to view her biography.
Why might some people say she was robbed of a Nobel Prize?
Watch Franklin’s X-ray diffraction pattern by clicking on the small X-ray diffraction picture.
What is x-ray crystallography (aka x-ray diffraction) ?
What did Franklin discover about the shape of DNA?
6. Linus Pauling ( http://www.dnai.org/timeline/index.html ) Watch the animation.
Linus Pauling proposed a structure for DNA that was incorrect. Describe Paulus’ structure and draw it below.
7. Maurice Wilkins (http://nobelprize.org/nobel_prizes/medicine/laureates/1962/wilkins-bio.html )
(http://www.nature.com/scitable/topicpage/maurice-wilkins-behind-the-scenes-of-dna-6540179 )
research, with the help from ________________, led to the discovery of the DNA molecule structure. This discovery was made by American biologist, ________________, and British physicist, ________________.
8. James Watson and Francis Crick ( http://www.dnai.org/timeline/index.html )
For what did they receive the Nobel prize? What year?
Describe the difference between Pauling’s structure and Watson and Crick’s structure.