DNA Technology: BACTERIAL TRANSFORMATION Ms. Gaynor Honors Genetics.
DNA: Deoxyribose Nucleic Acid The Genetic Material Chapter 2: Introduction to DNA Ms. Gaynor Honors...
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Transcript of DNA: Deoxyribose Nucleic Acid The Genetic Material Chapter 2: Introduction to DNA Ms. Gaynor Honors...
DNA: Deoxyribose Nucleic Acid
The Genetic Material
Chapter 2:Introduction
to DNA
Ms. Gaynor
Honors Genetics
DNA • Deoxyribose nucleic acid type of nucleic acid
– What is the other type of nucleic acid?
• RNA• DNA function
– to hold genetic code – Genetic code = genetic
instructions to make proteins
• DNA is found in nucleus of eukaryotic cells
• Found in nucleoid region in prokaryotes
The Short History of DNA and Genetics (Part 1)
•From 1866-1953
Searching for Genetic Material• Gregor Mendel
(1866): – discovered that
inherited traits are determined by discrete units, or 'genes,’ - passed on from the parents.
• Freidrich Miescher(1868): – discovered DNA– Isolated something
new from the nuclei of eukaryotic cells
• Later called DNA!!!
Searching for Genetic Material• Thomas Hunt Morgan (1910):
– Worked with fruit flies• Specifically eye color of these flies!
– Discovered genes are located (linked) on chromosomes
Searching for Genetic Material• Fredrick Griffith (1928):
– Studied effects of virulent (virus-causing) bacteria vs. nonvirulent bacteria injected into mice
– Used transformation:• Inserted foreign DNA and
changed protein/ trait
– believed that the transforming agent was an inheritance molecule.
Non-virulent vs. Virulent
Bacteria
SMOOTH:kill
ROUGH: harmless
BAD/HARMFULNOT HARMFUL/BENIGN
Griffith's Transformation Experiment
• Used the Pneumococcus bacteria – Include2 types:
•a virulent S strain with a Smooth coat– kills mice
•a non-virulent R Rough strain – does not kill mice.
• Heat destroys (kills) living cells!!!• When heated Smooth (harmful) cells
(DEAD) are mixed with living Rough (benign) cells and injected into mice, the mouse dies. – WHY?
http://www.quia.com/files/quia/users/hlrbiology/Animations/08_DNA_and_Proteins/Griffith_Mouse_Experiment.swf
Searching for Genetic Material
http://brookings.k12.sd.us/biology/ch12DNARNA/Chapter%2012A.mpg
Searching for Genetic Material
Oswald Avery, Colin MacLeod, & Maclyn McCarty (1944):
• Reported that “transforming agent” in Griffith's experiment was DNA.
• Also used the Pneumococcus bacteria and test tubes (NOT mice)
The Avery, et al. Experiment • Used S (harmful) strain
– Opened up the cells– Isolated
• DNA, proteins and other materials SEPERATELY
– Mixed R bacteria with these different materials– Only those mixed with DNA were transformed
into S bacteria.S DNA
+ R Bacteria
S PROTEINS +
R Bacteria
TEST
TUBES
OTHER S CELL PARTS
(sugar/RNA) +
R Bacteria
http://wps.aw.com/bc_russell_igen_me_1/
Discovering the Structure of DNA
Edwin Chargaff (1950)•Discovered a 1:1 ratio of adenine to thymine and guanine to cytosine in DNA samples from a variety of organisms.
Chargaff's Rule (Data)
Relative Proportions (%) of Bases in DNA
ORGANISM A T G C
Human 30.9 29.4 19.9 19.8
Chicken 28.8 29.2 20.5 21.5
Grasshopper 29.3 29.3 20.5 20.7
Sea Urchin 32.8 32.1 17.7 17.3
Wheat 27.3 27.1 22.7 22.8
Yeast 31.3 32.9 18.7 17.1
E. coli 24.7 23.6 26.0 25.7
Discovering the structure of DNA
Chargaff movie and Building Blocks movie
http://www.hhmi.org/biointeractive/dna/animations.html
Chargaff’s RulesA = TC = G
Discovering the structure of DNA
Maurice Wilkins (1952)• Photographed DNA using x-
ray crystallography• Worked with another
scientists named Rosalind Franklin
• Awarded the 1962 Nobel Prize for Physiology or Medicine with Watson and Crick
Linus Pauling’s TRIPLE helix
Pauling Triple Helix Model
http://www.hhmi.org/biointeractive/dna/animations.html
Linus Pauling(1954)
• proposed a triple helix structure for DNA
Discovering the structure of DNA
Rosalind Franklin (1952)
•Obtained sharp X-ray diffraction photographs of DNA (Photo 51)•Watson and Crick used her data revealed its helical shape
•Watson and Crick went on to win Nobel Prize (1962) for their DNA model
Photo 51
How did PHOTO 51 reveal DNA’s helical shape?
• X-rays passing through a helix diffract at angles perpendicular to helix making an "X" pattern, which favors an equal diameter "helix".
She finally gets credit Rosalind Franklin University of Medicine and
Science, located on Green Bay Road in North Chicago, Illinois
Searching for Genetic Material
Alfred Hershey & Martha Chase (1952)– Confirmed DNA was genetic material
– Used bacteriophages (viruses)
– HYPOTHESIZED DNA, not protein, is the hereditary material
Searching for Genetic Material
Hershey and Chase Experiment Animation
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html
Searching for Genetic MaterialHershey and Chase Experiment
Discovering the structure of DNA James Watson & Francis Crick (1953)
•Discovered double helix structure•Solved the three-dimensional structure of the DNA molecule
Watson Constructing Bair Pairs movie
http://www.hhmi.org/biointeractive/dna/animations.html