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DNA
Hmwk: take notes for an open note
quiz
• p. 287-290
• Focus: Who did the experiment?
•
What did they do? What did they
conclude? Key words/vocabulary.
Open note quiz p. 287-290
• 1. What disease was Griffith studying?
• 2. What did Griffith call the process by which
the harmless bacteria became harmful?
• 3. What was the purpose of Avery in repeating
Griffith’s experiment? In other words, what
did he want to know?
• 4. What was the conclusion of Avery’s
experiment?
• 5. A virus that infects bacteria is called a:
• 6. What did Hershey & Chase use to track DNA
and proteins?
Big ideas
• Living systems store, retrieve, transmit and
respond to information essential to life
processes.
• Biological systems interact, and these systems
and their interactions possess complex
properties.
Essential knowledge
• DNA and in some cases RNA, is the primary
source of heritable information
– Genetic information is stored in and passed to
subsequent generations through DNA molecules
– The proof that DNA is the carrier of genetic
information involved a number of historical
experiments: Watson, Crick, Franklin, Wilkins,
Griffeth, Avery
Essential knowledge continued
• DNA is composed of sugar, phosphate and
nitrogen base, which form nucleotides
• DNA is held together by covalent bonds and
hydrogen bonds
• DNA is antiparallel and double stranded
• DNA exhibits base pairing that is conserved
through evolution : A-T and G-C (Chargoff’s
rule)
Essential knowledge continued
• Purines & Pyrimidines differ in their carbon
rings
Learning outcomes
• Be able to explain the experiments &
conclusions of Griffeth and Avery’s research
using Pneumococcus & mice.
• Identify the 3 subunits of DNA & describe how
they are put together to construct an intact
molecule.
Learning outcomes continued.
• Understand the importance of Chargoff’s rules
& the complementary nature of base pairing.
• Describe Watson & Crick’s 3 dimensional
model based the evidence provided by
Rosalind Franklin.
1. What is DNA?
• 2. Deoxyribonucleic Acid
*. a chemical that stores genetic information
*. the instructional material
of chromosomes
* Blueprint of life
Griffith’s experiment
1. What experiments lead
scientists to believe DNA was the
“genetic material”? (read 287-290)
2. Griffith’s Transformation experiment 1928
* concluded: Streptococcus bacterial cells
can pick up “free” genetic information
* Griffith did not know the “free stuff” was
DNA.
Hypothesis: Material from dead cells can genetically transform
live bacterial cells.
Conclusion: A chemical substance from dead cells can genetically
transform live cells.
2. Avery– 1944
* used the same Streptococcus bacteria
strains (S & R) –
*stripped dead S (smooth virulent strain) of
protein
*R (rough non-virulent) still transformed
2. Hershey and Chase experiment
* Use radioactive markers to follow
proteins & DNA
•conclusion:
DNA enters BacteriaDNA is genetic
material
Animation
Quick check
• 1. What is DNA?
• 2. Describe the 2 strains of bacteria used by
Griffith.
• 3. What did Griffith do to the “deadly”
bacteria in the experiment?
• 4. What happened to the “good” bacteria
when mixed with the “deadly” solution?
• 5. Explain what is meant by “transformation”
with regard to the experiment.
• 6. How did Avery alter Griffith’s experiment?
What did he want to know that Griffith could
not conclude?
• 7. Explain how Avery was able to conclude
that DNA was the chemical that the bacteria
picked up and transformed them.
• 8. Explain how Hershey & Chase determined
that DNA entered the cell from the virus.
What has knowing about DNA
done for us?
Genetic disease knowledge/treatments
Identification of unknowns: military, 911, abductions
Exoneration from prison/ sentencing for prison
1. What is DNA’s structure?
2. DNA structure:
*made of monomers called nucleotides
* nucleotides are made of:
-5 Carbon sugar (deoxyribose)
- phosphate group (PO4)
- nitrogen base
Quick check
2. Nitrogen bases are specifically paired
-
Adenine –Thymine (2 H bonds)
-
Guanine – Cytosine
( 3 H bonds)
2. Nitrogen bases are grouped as
*purines (double carbon rings):
adenine & guanine
*pyrimidines (single carbon rings)
cytosine & thymine
Quick check
2. DNA is double stranded helix, with
anti-parallel strands
* 3’- 5’ strand
* 5’- 3’ strand
2. Phosphodiester bonds hold one nucleotide to
another –
Extract DNA
Lab:
• Use the knex to build a DNA model. Will do
tomorrow and 12.3
• Also assign a model making project… I like the
toothpick or bead activity.
Quick check
2. Nitrogen bases are specifically paired
-
Adenine –Thymine ( __ H bonds)
-
Guanine – Cytosine
( __ H bonds)
2. __________ bases are grouped as
*purines (________ carbon rings):
adenine & guanine
*pyrimidines (________ carbon rings)
cytosine & thymine
Quick check
Quick check
1. How was the structure of DNA
identified?
2. Erwin Chargoff:
*Chargoff’s rule : The proportion of adenine
equals that of thymine, and guanine equals
that of cytosine -- therefore, purines are
proportionate to pyrimidines
2. Rosalind Franklin:
* Used X-ray diffraction to determine
3 dimensional structure of DNA --worked with Maurice Wilkins
Photo 51
2. James Watson & Francis Crick:
*Used everyone else’s puzzle pieces (research)
to build a model of DNA’s structure -- 1953 --won Nobel Prize
• 2. Linus Pauling - 2 time Nobel Prize winner.....
COMPETITION!!!!
Video: Life story
• 20 minute recap of how DNA structure was
identified.
• P. 355-357 DNA fingerprinting
1. What is DNA fingerprinting and
what can we learn from it?
• What is DNA fingerprinting?
• - a method used to identify individuals based
on unique fragments of DNA (RFLP, VNTR, STR)
Secrets of the sequenceDNA/profiling
http://video.vcu.edu/vod/sosq/sosq_115_1.mp4
Timeline
• Day: What is DNA & why is it important? &
Experiments that identified DNA as the
genetic stuff.
• Day: What is DNA’s structure/function? Lots
of modeling, examples etc…. Provide
directions for building a DNA model at home.
• Day : Extract DNA (thymus, cheek cells, kiwi)
• Day: Build DNA model knex
• Day : Notes history of DNA/video clip…
• Day: DNA fingerprinting notes / online lab