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• If you were going to build something, what
is the most important item that you would
need? Explain why in at least 5 coherent
sentences.
DNA, RNA, &
PROTEIN
SYNTHESIS
DNA DISCOVERY
DNA DISCOVERY
Frederick Griffith-British
• Studied the cause of pneumonia and
possible vaccines.
• Discovered two strains, S and R.
• S-strain is live and causes disease. Named
for smooth sugar-coat colonies.
• R-strain does not cause disease and has
rough colonies without a sugar-coat.
Griffith’s Experiment
Observation:
Organisms are able to pass on their
traits to their offspring according to
the Laws of Genetics as developed by
Gregor Mendel.
Question:
What, within cells, serves as the
genetic code material?
Griffith’s Experiment
Hypothesis:
– By manipulating exposure to
different strains of bacteria, the
specific chemical within cells that
serves as the genetic material will
be isolated.
Griffith’s Experiment
Procedure:
• Griffith injected
some of the R-strain
bacteria into mice.
– What do you think
happened?
Griffith’s Experiment
• Griffith
injected some
of the S-strain
bacteria into
mice.
– What do you
think
happened?
Griffith’s Experiment
• Griffith knew that
polysaccharides are
not affected by heat,
so he used heat to
kill some of the Sstrain bacteria and
then injected them
into mice.
• What do you think
happened?
Griffith’s Experiment
• Keep in mind that neither
dead S-strain nor live Rstrain bacteria killed the
mice.
• Griffith then mixed some of
the heat-killed S-strain and
some of the live R-strain
bacteria and then injected
them into mice.
• What do you think
happened?
Griffith’s Experiment
Conclusion:
• The polysaccharide coating is not the
genetic material.
• When mixed, the R-strain bacteria
were able, somehow, to absorb
genetic material from the dead Sstrain and turn into S-strain
bacteria.
• This ability was subsequently named
transformation.
Griffith’s Experiment
Theory:
A specific chemical controlled the
transformation of cells.
DNA DISCOVERY
Oswald Avery-American
• Expanded on Griffith’s experiments.
Observation:
A specific chemical controls
transformation.
Question:
What chemicals are present in cells that
can control transformation?
Hypothesis:
Either protein, RNA, or DNA control cell
transformation.
AVERY’S EXPERIMENT
Procedure
• Using live S cells, Avery separately
destroyed the proteins, RNA, and
then DNA.
• These separate batches were mixed
with R cells again and injected into
the mice.
AVERY’S EXPERIMENT
• R-cell with no-protein S cells
= dead mice.
• R-cell with no-RNA S cells
= dead mice.
• R-cell with no-DNA S cells
= normal mice.
AVERY’S EXPERIMENT
Conclusion:
Without DNA, the S cells could not
transform the R cells. DNA must be
the transforming agent.
DNA DISCOVERY
Hershey-Chase Experiment- Americans
• Set out to determine if DNA or
proteins were hereditary material in
viruses.
Observation:
Previewed Griffith/Avery
experiment results.
HERSHEY-CHASE EXPERIMENT
Question:
What chemical allows a virus to
infect a bacterium?
Hypothesis:
If DNA and proteins are chemically
labeled, then the hereditary
chemical will show up in the
reproduced cells.
HERSHEY-CHASE EXPERIMENT
Experiment:
• Labeled virus proteins with radioactive
sulfur.
• Labeled virus DNA with radioactive
phosphorus.
• Allowed each sample to separately infect
E. coli.
• Once viruses are removed from the
bacterium, the bacterial cells could be
tested for each radioactive sample.
HERSHEY-CHASE EXPERIMENT
Conclusion:
The DNA had completely transferred, while
trace amounts of protein were present in the
new cells.
DNA….
-is the hereditary material in viruses.
-Controls and determines the traits of an
organism
-Maintains control by producing proteins
Proteins control all body processes.
Discovery of DNA
1. What makes the S strain bacteria virulent?
2. Why was Griffith’s Fourth experiment so
important?
3. What did the Hershey-Chase experiment
prove?
4. According to Avery, what is the role of DNA
during Griffith’s experiments?
5. List the steps of the Scientific Method.
DNA STRUCTURE
DNA STRUCTURE
• Consists of repeating subunits called
nucleotides
• Nucleotide parts are all held
together with covalent bonds
• Nucleotides have 3 parts:
– SUGAR
– NITROGENOUS BASE
– PHOSPHATE GROUP
DNA Nucleotide
DNA STRUCTURE
• Sugar: Deoxyribose, a 5
carbon sugar
• Phosphate Group: One
phosphorus atom with
four oxygen atoms.
– The phosphate attaches to
the deoxyribose at the
methyl group.
– This forms the backbone of
DNA.
DNA STRUCTURE
• Nitrogen Bases:
– Adenine, Thymine, Guanine, and Cytosine
• Nitrogen bases are carbon rings with
random nitrogen atoms
– Purines= double-ringed bases, Adenine and
Guanine
– Pyrimidines= single-ringed bases, Thymine
and Cytosine
DNA STRUCTURE
DNA STRUCTURE
DNA STRUCTURE
• Nitrogen bases stick out to the inside,
toward each other.
• Adenine always pairs with Thymine, and
Cytosine always pairs with Guanine.
• The base pairs are held together with
weak hydrogen bonds.
• The percentage of Adenine always equals
the percent of Thymine; Guanine
percentage always equals Cytosine
percentage.
Base Pairing
Stars represent
hydrogen bonds
DNA STRUCTURE
Two single strands of DNA are bound
together, forming a double-helix
The strands are complementary to
each other, not identical.
Watson and Crick first proposed this
theory of a double helix.
DNA Structure
1. Compare a purine to a pyrimidine.
2. Why does Adenine bond with Thymine and not with
Cytosine?
3. Weak hydrogen bonds hold the DNA helix together.
What is the importance of using weak bonds?
4. If 15% of the nucleotides in DNA are cytosine, what
percentage of the nucleotides are adenine? Why?
5. What types of bonds exist in DNA and where do they
work?
DNA Replication
DNA Replication
Chromosomes are long strands of DNA
that must be duplicated before cell
division.
Complementary strands of the double
helix must separate before
replication occurs.
Leading Strand
Lagging Strands
DNA Replication
These strands divide by breaking the
weak hydrogen bonds between the
nucleotides.
DNA Helicase is the enzyme that
breaks the hydrogen bonds between
the nitrogen bases.
-The area where the helix splits is
called the replication fork.
DNA Replication
DNA Replication
Free-floating nucleotides bind to the newly
uncovered nucleotide sequences.
DNA Polymerase is an enzyme that adds
the new nucleotides.
DNA Polymerase works in opposite
directions on the separated DNA strand.
DNA Replication
The double helix unzips entirely and
forms two identical double helix.
These two helices are each made of one
original strand and one new strand.
(Semi-Conservative Replication)
Replication
1. What makes DNA replication semiconservative?
2. Compare DNA Helicase to DNA
Polymerase.
3. How do the DNA polymerases travel on
the DNA strands?
4. How is eukaryotic DNA replicated so
quickly?
5. Compare the Leading and Lagging
Strands.
3
1
2
4
Protein Synthesis
Protein Synthesis
Directions of DNA
DNA follows a specific path to produce
proteins.
RNA is used as an intermediate to
proteins.
DNA > Transcription > RNA > Translation > Protein
Protein Synthesis
RNA vs. DNA
RNA has one strand… DNA has two
strands
RNA uses Ribose sugar….DNA uses
Deoxyribose.
Uracil replaces Thymine in RNA
RNA strands are very short, and DNA
strands are very long.
RNA with Uracil
RNA with Cytosine
RNA with Adenine
RNA with Guanine
Protein Synthesis
Types of RNA
mRNAMessenger RNA takes the directions of DNA
to the rRNA.
rRNARibosomal RNA uses the DNA code to produce
proteins.
tRNATransfer RNA brings amino acids together to
produce proteins.
Types of RNA
TRANSCRIPTION
John Kyrk Transcription
Transcription Animation
Simple Animation
TRANSCRIPTION
RNA Polymerase binds to a DNA
promoter region, which is a specific
DNA sequence.
– This causes DNA strands to relax
and unwind in one section.
TRANSCRIPTION
RNA Polymerase adds free RNA
nucleotides to begin producing an RNA
strand.
– This RNA strand is COMPLEMENTARY
to the DNA strand.
– Once the RNA Polymerase has finished,
the DNA retwists.
TRANSCRIPTION
A Termination Signal stops the RNA
Polymerase.
– This signal is another specific DNA
sequence.
– Both DNA and RNA strands are released.
– The new RNA strand can be rRNA, mRNA,
or tRNA.
– RNA strands are then manipulated in
Translation to make proteins.
Pre-mRNA Editing
1. 5’ Cap-
2. 3’ Tail-
3. Introns vs Exons
Transcription Practice
• DNA: AATCGA
• RNA:
• DNA: ATACGGACA
• RNA:
• DNA: TACGATCGCCGA
• RNA:
The Genetic Code
Translation Animation
The Genetic Code
A set of rules that govern how
nucleotide sequence correlates to a
specific amino acid.
Following Transcription, the mRNA
strand is “read” in units of three
adjacent nucleotides called a Codon.
The Genetic Code
CODONS are 3-nucleotide sequences on
mRNA that code for specific amino
acids or a start/stop signal.
Several codons may code for the same
amino acid, but each codon codes for
only one amino acid.
The Genetic Code
AUG is the universal START codon,
while UGA, UAA, and UAG are all
STOP codons.
Translation starts with start codons
and ends with stop codons.
Animation
TRANSLATION
TRANSLATION
A ribosome attaches to a strand of
mRNA, allowing a tRNA anti-codon
molecule to attach to the correct
mRNA codon.
The ribosome moves down the mRNA
from 5’ to 3’.
TRANSLATION
While the first tRNA molecule is
attached to the mRNA, the ribosome
moves down the sequence of
nucleotides.
When the ribosome moves, it allows
the next tRNA molecule to attach to
the next codon.
TRANSLATION
When two consecutive tRNA
molecules are attached to the mRNA,
peptide bonds form between the
carried amino acids.
Both remain attached to the second
tRNA molecule.
TRANSLATION
These steps continue producing a long
strand of amino acids until the
ribosome reaches a stop codon. This
releases the new polypeptide.
Translation components break apart
and the newly created protein is sent
to its final destination.
Protein Synthesis
1.
2.
3.
4.
5.
Contrast Codons and Anti-codons.
Compare Translation to Transcription.
What does the Genetic Code do?
What are the roles of each type of RNA?
How does a tRNA anti-codon sequence
compare to the original DNA sequence?
LINKS TO ANIMATIONS
•
http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.sw
f
•
http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf
•
http://www.johnkyrk.com/DNAreplication.html
•
http://learn.genetics.utah.edu/content/begin/dna/transcribe/
•
http://www.johnkyrk.com/DNAtranscription.html
•
http://www.biostudio.com/demo_freeman_protein_synthesis.htm
•
http://www.johnkyrk.com/DNAtranslation.html
CREDITS
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Outline information adapted from http://biology.clc.uc.edu/courses/bio104/dna.htm
http://porpax.bio.miami.edu/~cmallery/150/gene/sf11x1a.jpg
http://www.offresonance.com/wp-content/uploads/2008/05/450px-griffith_experimentsvg.png
https://filebox.vt.edu/users/mahogan2/Filebox%20Portfolio/Webquest%20for%20DNA_files/image004.jpg
https://www.msu.edu/course/isb/202/ebertmay/drivers/nucleotide.jpg
http://coris.noaa.gov/glossary/nucleotide_186.jpg
http://www.dnahandbook.com/s/10009/Images/purines.gif
http://www.brooksdesign-cg.com/Images/cg/SCdna6.gif
http://www.mariemontschools.org/halsall/images/dna_molecule.gif
http://porpax.bio.miami.edu/~cmallery/150/gene/c7.16.14.fork.jpg
http://www.elmhurst.edu/~chm/vchembook/images/582dnarepline.gif
http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-2/ch10_DNA-rep.jpg
http://www.biologycorner.com/resources/replication.gif
http://library.thinkquest.org/18617/media/replication-simple.gif
http://upload.wikimedia.org/wikipedia/commons/2/2c/RNA_chemical_structure.GIF
http://porpax.bio.miami.edu/~cmallery/150/gene/c7.17.7b.transcription.jpg
http://stardec.ascc.neu.edu/~bba/CBIO3580/DOGMA/Fig13_18.JPG
https://www.msu.edu/course/lbs/333/fall/images/geneticcode.gif
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Translation.gif
http://www.biologycorner.com/resources/translation_lettered.jpg