Transcript chapter 7: nucleic acids and proteins

CHAPTER 7: NUCLEIC
ACIDS AND PROTEINS
IMPORTANT QUESTIONS
ABOUT DNA
• How do we know that DNA houses the
genetic code?
• What is the structure or shape of DNA?
• What does DNA do? What is its’
function?
• How does DNA replicate?
• Who are the major characters on the
path to discovering the nature of DNA?
How do we know that DNA
is the code of life?
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Work of;
Griffith
Avery
Hersey &Chase
Frederick Griffith
• Researching
pnuemonia, 1928.
• Answered question
is it the protein or
DNA that holds the
genetic code?
• Remember, genes
are made of DNA.
TRANSFORMATION
• Transformation: a
strain of bacteria
(harmless) is
changed to another
strain (harmful) via
cell cycle.
• Griffith experiment
at right.
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Griffith
Experiments
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AVERY EXPERIMENTS
• 1944
• Discovered that DNA stores and transmits
genetic information.
• Took Griffiths’ experiments one step further.
• Blended bacteria with an enzyme that kills
different proteins present in the cells. The
strains were virulent.(deadly)
• Then he blended the bacteria with an
enzyme that kills DNA. The strain did not
grow into a killer strain.
• This added further proof that DNA was the
carrier of genetic blueprints.
AVERY EXPERIMENT
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HERSEY & CHASE
• 1952, American Scientists
• Bacteriophages, virus that
infect bacteria. Have a DNA
center with a protein coating.
• Wanted to know if these
virus were injecting protein
into the bacteria cell or DNA
into the cell.
• Used radioactive isotope as
a marker.
HERSEY & CHASE
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Who discovered the shape
of DNA?
• Many people were involved in the
discovery of DNA’s shape.
• Some people were overlooked in this
process.
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Who was Rosalind
Franklin?
• Worked during 1950’s
• Produced image of DNA
using x-ray crystallography
• This image led to the
discovery of the shape of
DNA. (double helix)
• Worked with Maurice
Williams
• Work was overlooked
during her time.
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Rosalind Franklin
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Watson & Crick
• James Watson, Francis
Crick
• Completed the first
model of DNA that
worked chemically.
• 1953, Double Helix
structure published in
Nature
• Won Nobel Prize
James Watson
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American Researcher that worked with
Francis Crick to determine the shape
DNA.
Wrote controversial book about the
process.
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Francis Crick
• Helped determine the shape of
DNA as well as the replication
process.
• Supported Rosalind Franklin
• Disagreed with Watson’s
interpretation of the race to find
the shape of DNA
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Structure of DNA
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Deoxyribonucleic acid
Made out of nucleotides
Only 4 nucleotides form DNA
Each contains Posphate group, sugar,
and nitrogenous base
Adenine, guanine, thymine, cytosine
BASE PAIRING
• DNA strands are
held by hydrogen
bonds
• The number of H
bonds are specific
for each amino acid
• G=C
• A=T
Chargaff’s Rule
• Erwin Chargaff,
American biochemist
• Figured out that in a
sample of DNA the
amounts of;
• G=C
• T=A
THE DOUBLE HELIX
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DNA REPLICATION
1. DNA helicase unzips the
DNA molecule
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2. Nucleotides are brought
in and create
complimentary base
pairs using covalent
bonds
3. DNA polymerase zips the
nucleotides together.
There are now two
daughter strands
Concept Review
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What is transformation?
What did Avery do?
What about Hersey Chase?
Who were the players in the race to find
the shape of DNA?
• What is the shape of DNA?
What are proteins?
• Polymers of amino acids
• Contain nitrogen, carbon, hydrogen,
and oxygen
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What are proteins for?
What is PROTEIN
SYNTHESIS?
• The process/method for making
proteins.
RNA-Ribonucleic Acid
• Acts as messenger between
DNA and the ribosome.
• Vital part of making proteins
from amino acids.
• Uses: Ribose = sugar, Uracil
pairs with Adenine, single
stranded helical molecule.
• 3 types of RNA: Messenger
RNA (mRNA), Transfer RNA
(tRNA), ribosomal RNA
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What is Transcription?
• Creates a complimentary strand of RNA
from a molecule of DNA.
• Takes the information of DNA and puts
into the form of RNA.
• mRNA can leave the nucleus and work
with the ribosome in the cytoplasm.
TRANSCRIPTION
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• Step 1.-RNA polymerase
unzips DNA molecule
• Step 2. - Complimentary
strand of RNA is created.
• Step 3.-the strand is edited
• Introns: parts removed,
non-coding
• Exons: useful parts of RNA
• Edited form of mRNA
leaves nucleus
What are proteins made of?
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• Polypeptide, chains of
amino acids.
• (20 different amino
acids)
• It’s the order of amino
acids that makes things
different!
• Read in triplets called
codon.
CODONS
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• Proteins are coded for
in 3’s, called the Triplet
Code.
• Codon = nucleotide
(sugar, phosphate
group, nitrogenous
base)
• Each codon codes for
a specific amino acid to
be attached to the
chain.
How to read the code…
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On to Translation….
TRANSLATION
• mRNA is “translated”
into a polypeptide
chain.
• Translated from one
language to another,
mRNA into tRNA/rRNA
that lead to proteins.
• Anticodon
TRANSLATION
• Step 1. Need to find start codon, AUG
• Step 2. mRNA and tRNA are brought together
and matched up according to complimentary
base pairing at the ribosome.
• tRNA has brought along an amino acid
• Step 3. The ribosome seals the mRNA and
tRNA together, the amino acids are joined
together in a chain through a polypeptide bond.
• Step 4. The process ends with the stop codon.
RIBOSOME
Figure 11-19Translation begins with the
attachment of a ribosome and the first tRNA to a
"start" (AUG) codon. The ribosome then moves
along the mRNA transcript. The polypeptide
elongates as an amino acid is added for each
codon. When the ribosome arrives at a "stop"
codon, the completed polypeptide is released.
Fairy Tale:
"Once upon a time there were two fraternal twin brothers: Donald N. Armstrong and Ronald
N. Armstrong. Donald was the smarter of the two, and he was a successful inventor with
many patents. Although Ronald was not as smart as his brother, he was extremely loyal. One
day Donald came up with an idea for a solar powered car. Given the ever-present possibility
of energy shortage, an efficient solar powered car would be in great demand. However,
Donald really didn't want to leave his comfortable estate. He certainly couldn't take a chance
by using e-mail or a fax to send his plans to the factory. They might be stolen by industrial
spies! Donald knows his loyal brother would do anything for him, so he asks him to be a
messenger and carry the plans to the factory. At the factory, the assembly line is set up and
factory workers bring the parts to assemble the prototype. The car proves to be enormously
successful. The Armstrong brothers buy an even bigger estate and live happily ever after!”
CHOICES:(Ron, car, factory, estate, plans,worker, Don)
DNA
mRNA
tRNA
Nucleus
Protein
Ribosome
Triplet Code
PROTEIN SYNTHESIS
• Can you
describe
each step of
the process
taking place
in this
diagram?
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