F. Griffith 1928 London (BACKGROUND)
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Pneumonia inflames your lungs then mucus to fill them up which causes them to stop breathing
o Pneumonia can be bacterial or viral
F. Griffith tries to make a vaccine against pneumonia
o Vaccine: the preparation of Attenuated germ
o Attenuated: died or weakened
When white blood cells encounter Attenuated germs the do phagocytosis creating a vacuole
around the germ. Then Lysosomes break the germ down.
o Once the germ is taken care of, the cell makes antibodies so it can easily fight against this
germ again.
F. Griffith bacteria experiment
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Smooth bacteria: encapsulated Ruff bacteria: not encapsulated
He injected a mouse with the smooth bacteria and it died
o The mouse died because the bacteria is virulent: harm causing
He injected a mouse with Ruff bacteria
o The mouse lived but it did get sick
He injected a mouse with capsuled bacteria that was killed by heat
o The mouse lives, nothing happens.
He injected a mouse with dead smooth bacteria and live ruff bacteria.
o The mouse dies
 They look at blood sampled of the mice. The saw that there were live smooth
virulent bacteria.
HIS CONCLUSION: he thought that capsule causes viral danger but he never figured out why.
The transformation agent is found 1949
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They said that DNA caused the formation of smooth bacteria
Some molecules survived heating process then went into ruff cells and changed their DNA
Bacterial Transformation: something is injected in a bacteria’s DNA which causes it to change
when it reproduces
Side things
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ATP is a nucleotide that is involved in RNA
Virus
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The only life function that has reproduce
o They need a host cell to reproduce
Virus: a parasitic structure
o Parasitic: depends on host cell
The virus only attacks a certain cell but the virus to cell relationship varies
There are viruses that only attack bacteria
o Tail fibers are used to attach to host, and the DNA in the head moves into cell
Bacteriophage: a virus that eats bacteria to live but eventually kill cell by doing so (in short these
viruses are called phage)
 The coat was made up of protein
 The core was made up of DNA
Lytic (used in Hershey)
 Approaches cell attaches to bacteria then injects DNA
o Now can use enzymes to make viral DNA and proteins for outer coat
o The DNA makes virus shells and new DNA
 These components make new virus which
Produce enzymes to destroy cell
 Lysogenic
o It injects its DNA into a bacteria and it attaches to chromosomes
 When it is in chromosomes it is called prophage and can be there for years doing
nothing
 At one point it can unattached and do what lytic does
 Cell can divide spreading it
 Cest (hand writing) but straight
o Generates but Moderate
o Do we have a sheet on this
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Weird things about viruses
 Some have single strain DNA or RNA
 Some have Double strain DNA or RNA
S. Lunia and M. Delbruck 1940’s (so what did they really do)
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They saw that DNA can be understood from viruses
They categorized viruses T1…..T7
They organized the viruses in Odd and Even groups.
o Because they saw that T2 T4 T6 were one group
T4 was a weird virus, under an electron microscope it looked as if it were a spaceship
o They thought this would help them find out if it was protein or DNA that passed on
genetic information.
 The problem was they knew that DNA only had 4 groups and amino acids had 21
R’
Hershey-Chase experiment background
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Scientist were never sure what held genetic information they thought maybe it was DNA or
Proteins
DNA: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphate
Protein: Carbon, Hydrogen, Oxygen, Nitrogen, and Sulfur
Some experiments were done by Avery but they were very complicated which made it bad
evidence
Hershey-Chase experiment (what holds genetic information)
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They take T4 bacteriophage
o DNA: They make one bacteria Phosphate radioactive (32P)
o Protein: They make a different bacteria’s Sulfur radioactive (31S)
 They did this by growing T4 in a radioactive environment
They put one bacteria in a test tub with E-coli (bacteria) so the virus will inject the bacteria
o In order to detach the viruses from the bacteria, they agitated the virus by shaking it.
Then they totally separated them by putting them in a centrifuge.
Tube with radioactive DNA: the pellet was radioactive
Tube with radioactive Protein: the pellet was not radioactive
E. Chargaff: background
Pyrimidines
small nucleotides
one ring
Cytosine, Thymine, and Uracil (CUT)
Two hydrogen bonds
E. Chargaff: discoveries
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Purines
large nucleotides
two rings
Adenine and Guanine (AG)
Three hydrogen bonds
He collect many nitrogenous bases
He said no matter what Organism the DNA is from it always has the same amount of
o Thymine to Adenine
o Guanine to Cytosine
He never saw the same amount of A to C
He said DNA is two nanometers throughout
More on DNA
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Nitrogenous bases bond with Hydrogen bonds so it can unzip allowing mRNA to copy it or so it
can be transcribed
Base pairing: Strains are complementary and anti-parallel
o A to T & G to C
Watson and Crick: background
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Watson: American biochemist went to Cambridge for doctorate work
Crick: British Physicist
Linus Pauling of Caltech discovered alpha helix and beta pleated sheets
Watson and Crick: research
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Every day they would come and talk to each other about other scientist’s research
From Linus Pauling’s discoveries they became a strong believer of the correlation
between Structure & Function
They knew DNA was very big and it had to coil like proteins do. But it was two strains so it had
to be double.
They also said DNA can be copied and it can be changed by mutations
o
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Watson and Crick theft
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They went to Kings college in London where they stole X-ray diffraction data from Rosalind
Franklin
 Ray diffraction ( X-ray Crystallography)
o You let DNA dehydrate so it shrinks and it become crystal
 They mix chemicals with it to create crystal fibers.
o Mount it on a sheet then shoot X-ray at it
 The photons then scatter in the crystal formal object (DNA
o Photographic paper is behind it which captures the image
 The X picture proved that DNA was a double helix
 Crick and Watson created a model of DNA and received a noble prize after Franklin died
DNA duplication
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DNA has instruction to make up proteins
It never comes out of the nucleus because it is too wide to exit nuclear pours
o RNA is singled strained so it can exist and enter nucleus
DNA synthesis: replication of DNA
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A cell can only divide one time so it duplicates its DNA once before the cell splits
DNA uncoils
The strains separate with the help of enzymes
o Organ of replication: the place where it splits
 Helicase is the enzyme that splits DNA
Super coil: When a section uncoils the parts over and under it coil a lot more
o There are other enzymes that stop this by snipping above and under the replication bubble
 Replication fork: the ends of the bubbles
Brace forms- stop it from coiling
DNA polymerase attaches to both sides of open DNA
o Its starts to read opened bases then brings complements
 Free nucleotide in DNA must have the correct sugar
o more bases add when duplicated cause the replication bubbles to spread even more
o The two strains at end on part of each is the original
o Semiconservative replication: keeps part of original DNA
o Template- model which we make new stuff from DNA or RNA
Nucleotides go to template with 3 phosphate groups because it needs the energy
o The 2 top phosphate groups break off and an exergonic reaction happens
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𝑒𝑛𝑒𝑟𝑔𝑦 𝑙𝑒𝑎𝑣𝑒𝑠
A-P~P~P→
A-P + Pi + Pi
 There is a very low chance of this falling back
 Cause this to make a strong covalent bond between the phosphate group and a
different deoxyribose
 The copy the DNA in small section normally of 2
Okazaki fragments: short, newly synthesized DNA fragments that are formed on
the lagging template strand during DNA replication. They are complementary to the
lagging template strand, together forming short double-stranded DNA sections.
DNA duplicates before cell splits
de novo is a Latin expression meaning "from the beginning," "afresh," "anew," "beginning
again
RNA (Ribonucleic acid)
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singled strained
has one more oxygen in sugar then DNA
urinals is in place of thymine
mRNA (messenger) , rRNA (ribosomal) , and tRNA (transfer)
RNA synthesis or transcription
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transcribe: to make almost the same copy
o Inactive strain: the DNA strain not getting transcribed
In prokaryotic cell happen in the part of the cytoplasm called nucleoid.
RNA POLYMRTASE: the enzyme that does the transcribing by putting the nucltiotides on the
DNA.
Protein synthesis background
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rRNA does note really function it is part of the structure for ribosomes
Ribosome is the non-membrane bond two part organelle that makes proteins
o Since it is non-membrane bond it is found in all cells
Subunits of Ribosomes: each is made up of specific proteins and rRNA in a specific mix
o Small subunit
o Large subunit
How did they find out which subunit was bigger
o Sedimentation: something falls to the bottom layer
 Measured in S units
o Large subunit S unit is 50
o Small subunit S unit is 20
o Whole ribosome S unit is 80
 Shape of structure cause it to move less efficient there is more resistance
Shape of Ribosome
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Subunits of Ribosomes: each is made up of specific proteins and rRNA in a specific mix
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Small subunit
 Has a binging site for new mRNA
Large subunit
 has a two binning sites for tRNA
 P (peptide) site
 A (amino) site
tRNA
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Short single strains about 85 pairs
o It folds on itself
Anticodon: three nitrogenous bases that binds to the mRNA
tRNA transfer specific amino acids to the ribosomes
parts of tRNA look complementary to each other
what do other loops do
mRNA function in Protein synthesis
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mRNA goes between the large subunit and the small subunit of the Ribosome with a code of the
sequence of nitrogenous amino acids
o tRNA’s anticodon is complementary to the mRNA’s codon this allow many amino
acids to join in the same order since the tRNA carries an amino acid depending on its
anticodon
Protein synthesis code
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people knew that DNA carried the information to make proteins but they wondered how do 4
nucleotides make so many proteins
o you need at least 20 codes of DNA to make all 20 amino acids
o some people thought it worked by the pairs of nitrogenous bases but that would only
make 16 and nitrogenous bases have to match
so people thought that it was in pairs of three which are called a codons
o that makes 64 codes for amino acids 4*4*4 = 64
o more info on homework
 that is because there is more than one code for the same protein
Stop codons: they are codons that are last in a polypeptide chain they stop knew amino acids from
adding on
o UGA: metline
o UAA: hisline
o UAG: tyrline
 Now there are only 61 amino acids
There are some amino acids that have 6 codes for them
o Serine and Argine
Genetic code is degenerate
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In physics it means more than one meaning (this is true in all cells)
 There is more than one code for an amino acid because if there is a mistake in
one code the cell can just use the other
Protein synthesis (translation)
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1)
You take nucleotide to write amino acid order
The amino acids are made in the cytoplasm if they are not consumed
There are dedicated parts of the DNA for mRNA and tRNA
There are 4 steps
Initiation (hand out)
 In cytoplasm
 The 5’ end is the front of the mRNA that is being pulled through
1. mRNA goes on small subunits binding site
2. The tRNA anticodon binds to the mRNA’s codon and is carrying a Methionine
a. Modified Methionine shows use a new protein is being made
3. The large subunit then attaches and the tRNA is in the P site
2) Elongation
 This is the longest step
 The poly petite chain is being made
 Uses enzymes as biocatalysts to bind each amino acid to one another
 Amino acids bind by dehydration synthesis
1. A knew tRNA with an amino acid goes into the A site
2. The amino acid binds to the amino acid that is held by the tRNA in the P site
3. The P site tRNA leaves leaving its amino acided bond to the other
4. The whole ribosome shifts and the new tRNA is now in the P site with two amino acids
! This process happened hundreds of time until the amino acids sequence is finished then
Termination accurse
3) Termination
 This ends the making of the amino acid chain
 A stop codon ends the process
o tRNA does not have an anticodon that is complementary to the stop codon
 After the polypeptide is made into a protein in the cytoplasm
1. A stop codon is in the mRNA strain
2. A protein called the release factor goes into the A site and block it up
3. The tRNA leaves
4. The top part of the ribosome detaches from the complementary bottom ribosomes
5. mRNA leaves and goes to other ribosome ( 4 and 5 which order) (how does the top
Ribosome bind to the bottom)(how does the tRNA get in and out) (for the stop codon
does the release factor bind to it)
4) After the polypeptide chain is made
 The other steps happen
 The proteins then go to the Golgi and are packed modified and sent out.
o Carbs are added or identification
Polysome: many Ribosomes that translate the same mRNA at the same time
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First ribosome starts (it has less of a chain)
More on DNA
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