History Of DNA Notes The Search and Discovery of Genetic Material.
-
Upload
pauline-farmer -
Category
Documents
-
view
216 -
download
0
Transcript of History Of DNA Notes The Search and Discovery of Genetic Material.
![Page 1: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/1.jpg)
History Of DNA Notes
The Search and Discovery ofGenetic Material
![Page 2: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/2.jpg)
Search For Genetic Material
• Scientists prior to 1940s believed proteins were the genetic material
• Early discoveries– Levene (1919): discovered nucleic acids – Griffith (1928): discovers transformation – Avery (1944): discovers that DNA is the
transforming agent.
![Page 3: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/3.jpg)
Levene: 1919
• Major Discovery:– Nucleotides contain: Sugar, phosphate
and one of four nitrogen containing bases
– Thought the bases were present in equal amounts (which is incorrect)
• Levene, however, thought this was too simple to store genetic code and his work was largely discredited at the time.
![Page 4: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/4.jpg)
Griffith’s Experiment: 1928
Discuss: Why do you think
this occurs?
Major Discover: There is a “transformation principle” that can transfer genetic information
![Page 5: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/5.jpg)
Avery 1944
• Using Griffith’s to isolate what the “transforming principle”
• Isolated Cells of the infectious strain– Used enzymes to digest and remove:
• Outer sugar coating• All proteins• All RNA
– Left with only DNA: was still able to transform harmless strain.
Discuss: What do you think this discovery meant?
Major Discovery: DNA carries the genetic information!
![Page 6: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/6.jpg)
Discovering DNA’s Structure Key People and Places
![Page 7: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/7.jpg)
Hershey-Chase Experiment: 1952• Major Discovery:– Confirm DNA carries
information and protein.
![Page 8: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/8.jpg)
Chargaff: 1949
• Looking at possible differences in DNA among different species.
• Major Discovery– “Chargaff’s Rule”: • amount of adenine (A) is usually similar
to the amount of thymine (T)• amount of guanine (G) usually
approximates the amount of cytosine (C).
![Page 9: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/9.jpg)
If the amount of:A is the same as TG is the same as CWhat would you assume about DNA structure?
Discuss:
![Page 10: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/10.jpg)
The RACE begins
• In the 1940s/early 1950s, what did scientists know:
– about genetic information? – What do you think they might be “racing” to
figure out? • Answer? They knew the make up of DNA
and of its genetic importance, but they now were racing to discover the STRUCTURE
Discuss this with
your tablemates
![Page 11: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/11.jpg)
The Contenders
Pauling
Watson and Crick
Franklin and Wilkins
![Page 12: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/12.jpg)
Rosalind Franklin: 1952• At this time, women were not highly
regarded in the scientific world.• Franklin worked with many men,
like Wilkins who saw her as an “assistant”
• Major Discovery:– She used x-ray crystallography to take pictures of DNA at different angles
Discuss: why might this be important?
![Page 13: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/13.jpg)
Pauling 1953• Linus Pauling was at the forefront of chemistry– very interested in protein – “wrote the book” on chemical bonds
• Major Discovery: Knew the three components of nucleotides; Pauling believed the structure of DNA to be an alpha helix
INCORRECT
![Page 14: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/14.jpg)
Watson and Crick:1953• Eccentric scientists whoworked together to put information for multiple sources together:– Levene: nucleotides contain 3 parts– Griffith/Avery/Hershey-Chase: DNA carries genetic
code– Chargaff: A + T and C + G– Franklin: helix structure
from x-ray photos
Discuss: Why might sharing data
be important in
science?
![Page 15: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/15.jpg)
Watson and Crick’s Major Discovery
![Page 16: History Of DNA Notes The Search and Discovery of Genetic Material.](https://reader038.fdocuments.in/reader038/viewer/2022110101/56649e685503460f94b63eb0/html5/thumbnails/16.jpg)
TIME LINE
1919 1928 1944 1949 1952 1952 1953 1953
Hershey-Chase
AveryLevene
Griffiths
FranklinChargaff
Pauling
Watson-Crick
With you group:
complete the timeline with the
people and their
major discoveries