Download DNA: The Genetic Material

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BIOL 230: Cell & Molecular Biology
Spring 2017
17-209
T, Mar. 14
1. Pre-Lab writeups due each Tues. (for T&R!!) at the start of lab.
(briefly, What? Why? How? for each expt.). Q & Hypothesis?!
2. Earn Extra Credit!! STEM Speaker Series: Wed. 5–6 pm; February
8th, – March 29th, 2015 (except March 8th - Flex Day). Bldg 6, Rm 101.
3. Lab this Week -- Thurs.: Expt. 8 – Photosynthesis!! 
4. REPORT TOPICS TODAY on WebACCESS!! (TurnItIn.com link).
Few sentences – be SPECIFIC about the focus of your topic, and give at least 1
professional sci. reference!
5. LAB REPORT INSTRUCTIONS are updated!!
(“Add’l Materials”). Report (in pairs) Due THIS Thursday, 3/16!!
6. Midterm #1 was returned!!
 M/C answer key will be found under “Additional Materials” on my website.
 Students scoring <70% on the exam must meet with me ASAP after reviewing your exam!
7. QUIZ #3 due TONIGHT!! (first attempt!)
REVIEW
1. Ch. 10: Diagram and explain how light-harvesting pigments capture light, and
how this is converted to cellular energy by noncyclic photosynthesis.
2. *** Compare & contrast the energy conversion mechanisms of cellular
respiration and the light reactions of photosynthesis. What energy inputs &
outputs are used, and in what forms?
TODAY’s Objectives: Students should be able to....
1. Describe and diagram the relationship between the light reactions and the
“dark” reactions of photosynthesis.
2. Ch. 13: Describe the separate experimental processes by which Griffith,
Avery et al., and Hershey/Chase proved the identity of the Genetic
Material.
3. Describe five pieces of evidence (and the scientists that produced them)
that Watson and Crick used to deduce the structure of DNA.
4. Diagram and describe 6 structural characteristics of DNA that are
important to its function. ****
 These objectives are your HOMEWORK between classes!!!
 DUE every Thurs. at the end of lecture!!
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Fixation of CO2:
The Calvin–Benson Cycle
• The Calvin–Benson cycle consists of
three processes:
1. Fixation of CO2, by combination with RuBP
(catalyzed by RUBISCO).
2. Conversion of fixed CO2 into carbohydrate
(3PG) (this step uses ATP and NADPH).
3. Regeneration of the CO2 acceptor RuBP
(5/6 of the carbon fixed!!!) by ATP.
C. The Calvin–Benson Cycle:
Products
• The end product of the cycle is
glyceraldehyde 3-phosphate, G3P.
• There are two fates for the stored G3P:
 1/3 ends up as starch, which is stored in the
chloroplast and serves as a source of glucose.
 2/3 is converted to the disaccharide sucrose,
which is transported to other organs.
http://www.science.smith.edu/departments/Biology/Bio231/calvin.html
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Figure 10.15
The Calvin-Benson Cycle
1C
5C
[6C]
3C
3PG
5C
G3P
Making Carbohydrate from CO2:
The Calvin–Benson Cycle
• Products of the Calvin–Benson cycle:
– are vitally important to the biosphere:
– they are the total energy yield from sunlight conversion by
green plants.
• Most of the stored energy is released by the
plant’s own Glycolysis & Cellular Respiration.
– Some of the carbon of glucose becomes part of amino
acids, lipids, & nucleic acids.
– Some of the stored energy is consumed by
heterotrophs, where glycolysis and respiration release the
stored energy.
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10.6) Metabolic Pathways in Plants
1. Green plants are autotrophs = “Producers”!!
– synthesize all their molecules from 3 simple starting materials: CO2, H2O, & NH4.
2. To satisfy their need for ATP, plants, like all other organisms,
carry out cellular respiration.
– Both aerobic respiration and fermentation can occur in plants
– respiration is more common.
3. Cellular respiration takes place both in dark and in light.
4. Photosynthesis and respiration = closely linked by the Calvin–Benson cycle.
– Some G3P from Calvin–Benson  pyruvate, the end product of glycolysis.
5. Some G3P  hexose phosphates, which can enter glycolysis.
– Once carbon skeletons from the Calvin–Benson cycle enter glycolysis
and the TCA cycle, they can be used to make lipids, proteins, and
other carbohydrates.
Figure 10.20 Metabolic Interactions in a Plant Cell
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Metabolic Pathways in Plants
1. Energy flows from sunlight
to reduced carbon in
photosynthesis to ATP in
respiration.
2. Energy can be stored in
macromolecules such as
polysaccharides, lipids, and
proteins.
3. For plants to grow,
a) energy storage must
exceed energy released or
b) overall carbon fixation by
photosynthesis must exceed
respiration.
4. The capture and movement of
sun energy becomes the basis
for ecological food chains.
Chapter 13: DNA &
Its Role in Heredity
1. DNA: The Genetic Material
2. The Structure of DNA
3. DNA Replication
4. The Mechanism of DNA Replication
5. DNA Proofreading and Repair
6. Practical Applications of DNA Replication
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13.1) DNA: The Genetic Material
• Nuclear transplantation
experiments (1930s):
– the nucleus carries
the genes!!!
• Joachim Hammerling:
• Algae - “giant cells”
• Acetabularia…..
• Animals –
– frogs, sheep, cattle….
DNA: The Genetic Material
figure 16-04 (2004)
1. Nucleus from somatic (“body”,
udder) cell of Species 1
2. Implanted in enucleated,
fertilized egg of Species 2
3. Offspring Genetically identical to
species 1 !!
FYI: http://www.dnalc.org/cloning.html
(Hello, Dolly!)
http://learn.genetics.utah.edu/units/cloning/index.cfm
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DNA: The Genetic Material
• Nuclear transplantation showed that
the nucleus carries the genes
• Staining reveals the “nucleic acids”
within the nucleus (Feulgen’s Dye)
• Different amounts in different species
• Half the amount in eggs and sperm
• (haploid gametes vs. diploid adult)
• Three experiments then proved
DNA is the genetic material: ……
FYI:
http://www.wwnorton.com/college/biology/discoverbio3/
core/content/ch12/animations.asp
A. Griffith: The “Transforming
Substance” is the Genetic Material
1. Frederick Griffith (1920s)
– DNA from a virulent strain of pneumococcus
genetically transformed nonvirulent bacteria into
virulent bacteria. (Streptococcus pneumoniae)
Tutorial: http://nortonbooks.com/college/biology/animations/ch12a01.htm
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Griffith’s Experiments
MOUSE
INJECTIONS:
Heat-kill virulent S
Killed S + Live R
1. Living S  death
2. Living R 
healthy
3. Heat-killed S 
healthy
4. Killed S + Live R
 Dead!!
• Something from
the dead S cells
TRANSFORMED
the harmless R
cells into
Killers!!!
• (smooth with
polysaccharide
capsule)
What is the “Transforming Principle”?
1. Griffith: partially purified “Transforming
Substance” caused the same transformation from
RS bacteria.
– Was mostly DNA!
2. Oswald Avery, Colin MacCleod & Maclyn McCarty
(1944): treated “TS” with various, highly-specific,
macromolecule-degrading enzymes
– (Proteases, RNAses, DNAses, Glycosidases, Lipases)
– None, except DNAses, removed the transforming
ability of the Transforming Material
– Therefore, DNA Must be the Genetic Material!!!
• Still, many detractors remained!!!…(“Still protein contaminant”)….
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B. Avery, MacLeod, McCarty Experiment
• Individually treated the TS with different procedures to remove
each known type of macromolecule…..
& glycosidases,
lipases
1. TS = genetic material (Griffiths)
2. TS = DNA
3. Therefore, DNA = Genetic
material!!
C. Hershey & Chase Blender Expt:
Prove DNA = Genetic Material!
• Alfred Hershey, Martha Chase (1952):
– Labeled viruses were incubated with host
bacteria.
 Labeled viral DNA entered host cells, while
labeled virus protein did not.
• Entry of the viral nucleic acids produced
hundreds of label-bearing viruses.
http://highered.mcgraw-hill.com/olc/dl/120076/bio21.swf
Original paper: http://www.jgp.org/cgi/reprint/36/1/39
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T2 Bacteriophage
“Bacterium-Eater” Life Cycle
Figure 11.2 (2004, 7e)
Fig. 13.3
Bacteriophage T2 Reproduction Cycle
1. Adhesion: Virus attaches
at specific host surface
receptor
2. Infection: Injects genetic
material
3. Synthesis & Assembly:
Virus particles replicate and
assemble (“mature”)
4. Release: About 100 phage
particles lyse host and
escape to reinitiate cycle
• Which part of the virus is
the genetic material that is
injected into cells???
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Hershey-Chase
Blender Expt.
•
32P-DNA
(Cells!!)
in Pellet
– Labels Phosphates
– (In DNA, not Protein!!)
•
32P
= DNA
(in pellet)
35S-Protein
in
supernatant (not in
cells!).
– Labels methionine and
cysteine amino acids
– (not in DNA!!)
• Thus, DNA is the
injected, Genetic
Material!!
35S
= Protein
(in sup. only)
Protein 
injected!
DNA =
injected!
13.2) The Structure of DNA
1. X-ray crystallography showed that the DNA
molecule is a helix (cylindrical spiral).
• (Rosalind Franklin, Maurice Wilkins).
2. Also, has regular diameter (~20 Angstroms = 20 Å)
• [= width of two purine/pyrimidine nucleotide pairs!! = 2 strands.]
3. Also: Density Centrifugation data  2 strands!!
http://www.dnai.org/a/index.html
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Composition of DNA was known
(Edwin Chargaff, 1950)
4. DNA is composed of
nucleotides
• (“Phos-Sug-Base”)
5. Each containing
Adenine, Cytosine,
Thymine, or Guanine.
a) [A] = [T]
b) [G] = [C]
c) [Pur] = [Pyr]
• Chargaff’s laws proven in
dozens of different species
The Structure of DNA
James Watson & Francis Crick proposed:
1. DNA is a double-stranded helix
2. with antiparallel strands, and
3. with bases linked by hydrogen bonding.
 Their model accounts for:
1) Storage of genetic information,
2) Possibility of mutation, and
3) How replication functions with DNA.
 ** All are required functions of the Hereditary Material!!
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Fig. 13.8
DNA Is a Double Helix
10 bp/turn
Tutorial:
http://www.mcb.harvard.
edu/Losick/images/Trom
boneFINALd.swf
0.34 nm
13.2) The Structure of DNA
1. X-ray crystallography showed that the DNA
molecule is a helix (cylindrical spiral).
• (Rosalind Franklin, Maurice Wilkins).
2. Also, has regular diameter (~20 Angstroms = 20 Å)
• [= width of two purine/pyrimidine nucleotide pairs!! = 2 strands.]
3. Also: Density Centrifugation data  2 strands!!
http://www.dnai.org/a/index.html
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Composition of DNA was known
(Edwin Chargaff, 1950)
4. DNA is composed of
nucleotides
• (“Phos-Sug-Base”)
5. Each containing
Adenine, Cytosine,
Thymine, or Guanine.
a) [A] = [T]
b) [G] = [C]
c) [Pur] = [Pyr]
• Chargaff’s laws proven in
dozens of different species
The Structure of DNA
James Watson & Francis Crick proposed:
1. DNA is a double-stranded helix
2. with antiparallel strands, and
3. with bases linked by hydrogen bonding.
 Their model accounts for:
1) Storage of genetic information,
2) Possibility of mutation, and
3) How replication functions with DNA.
 ** All are required functions of the Hereditary Material!!
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