Information flows from

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The Central Teaching of Molecular Biology
Information flows from DNA to RNA to PROTEIN
DNA
Translation
Construction
RNA
Transcription
PROTEIN
Blue Print
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1- DNA
1-DNA
Transcription
2- Synthesis of mRNA in the nucleus
2- Synthesis of mRNA in the nucleus
3- mRNA
3- mRNA
Nucleus
Cytoplasm
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Nucleus
Cytoplasm
mRNA
4- Movement of mRNA into cytoplasm via nuclear
pore
4- Movement of mRNA into cytoplasm via nuclear
pore
Ribosome
5- Synthesis of Protein
5- Synthesis of Protein
Translation
6- Polypeptide
6- Polypeptide
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The Genetic Code Nucleic Acids

• DNA and RNA are called Nucleic Acids.
• Nucleic Acids store information in the
  form of a molecular language.
• The language or code that is written into and
  read from Nucleic Acids is called the genetic
  code.

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Historical Moments in the Discovery of Nucleic
Structure
Between 1949 and 1953, Erwin Chargaff analyzed
the nucleotide base compositions of DNA
molecules found in human beings and a number of
other organisms as well.
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The four nitrogenous bases in DNA are
adenine (A)
thymine (T)
O
NH2
H
H3C
N
N
N
H
O
H
N
N
H
Purine bases
N
Pyrimidine bases
H
H
O
NH2
H
N
H
N
N
H
N
H
O
NH2
H
N
N
H
H
guanine (G)
cytosine (C)
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A
T
C
G
What conclusions could you make from Chargaffs
Data?
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Historical Moments in the Discovery of Nucleic
Structure
In 1950, after analyzing the data, Erwin Chargaff
reported that even though the DNA composition
varied from one species to another he suggested
that there was a pairing of complementary
nucleotide bases (A to T and G to C) in the DNA
molecule.
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Historical Moments in the Discovery of Nucleic
Structure
Between 1948 and 1952, Linus Pauling
discovered the role hydrogen bonding played
in the complex helical structure of polypeptides
and proteins. His structural discovery, called
the alpha-helix earned him the Nobel Prize for
Chemistry for his work on molecular bonding and
structure, especially in proteins.
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Polypeptide
Hydrogen Bonds
alpha-helix
Protein
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Historical Moments in the Discovery of Nucleic
Structure
Between 1950 and 1953, Rosalind
Franklin and Maurice Wilkins took
x-ray crystallographs (a
form of microscopic photography) that
showed that the mysterious molecule DNA had
a spiral shape. They were awarded Nobel Laureates
for their efforts.
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Twin Scaffolding Sugar Spirals
Center Vertical Axis
Paired Bases
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Historical Moments in the Discovery of Nucleic
Structure
In 1953,
James Watson Francis Crick put
all the pieces of scientific data
together and unscrambled the complex chemical
structure of DNA for which they also were
awarded Nobel Laureates.
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Watson Cricks DNA Model

• Pairing of complementary nucleotide bases
  Chargaff  

•  Base pairs combine using hydrogen
  bonds Pauling

• The DNA molecule has a spiral shape Franklin
  Wilkins

• The spiral is a double alpha-helix Pauling

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End of Introduction to the Central Dogma of
Biology
Beginning of the Structure of Nucleic Acids and
DNA
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Nucleic Acids are Polymers

• A polymer is a large molecule consisting of up
  to millions of repeated linked molecular
  units that are relatively light and simple.
• Each simple molecular unit is called a monomer

T
U
P
Ds
P
Rs
DNA monomer
RNA monomer
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Nucleic Acids are Polymers
Monomeric units are made up of an
information carrying nitrogen Base
a sugar Scaffold to hold the base
a phosphate Connector
Scaffold
Base
Connector
Rs
P
Ds
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• Nucleic acids (DNA and RNA) are composed of 4
  different nitrogenous bases

NH2
O
H
H3C
N
T
N
N
A
H
O
N
H
H
N
N
H
H
NH2
O
H
H
N
N
N
C
G
H
O
N
H
N
NH2
N
H
H
purines
pyrimidines
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• Each have H bond donors and acceptors

NH2
O
H
H3C
N
T
N
N
A
H
O
N
H
H
N
N
H
H
NH2
O
H
H
N
N
N
C
G
H
O
N
H
N
NH2
N
H
H
purines
pyrimidines
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• A-T base pairs form 2 H bonds
• G-C base pairs form 3 H bonds

NH2
O
H
H3C
N
T
N
N
A
H
O
N
H
H
N
N
H
H
NH2
O
H
H
N
N
N
C
G
H
O
N
H
N
NH2
N
H
H
purines
pyrimidines
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In RNA the base Thymine (T) is replaced by
Uracil (U)
NH2
U
T
N
N
A
H
N
H
N
H
NH2
O
H
H
N
N
N
C
G
H
O
H
N
N
NH2
N
H
H
purines
pyrimidines
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In DNA the scaffold is 2-deoxyribose, a pentose
(five carbon) sugar
In RNA the scaffold is ribose, a pentose (five
carbon) sugar
5
5
O
O
OHCH2
OH
OHCH2
OH
1
4
1
4
H
H
H
H
H
H
H
H
3
2
3
2
OH
OH
H
OH
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O
In both DNA and RNA the base is connected to the
1 position of the scaffolding sugar
H3C
H
N
O
N
H
H
O
5
OHCH2
OH
1
4
H
H
H
H
3
2
H
OH
(liberating water - dehydration synthesis)
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In both DNA and RNA a phosphate connector is
added to the 5 position of the scaffolding sugar
O
H3C
H
N
O
N
H
O
5
O
P
O-
OHCH2
O
O
1
4
O-
H
H
H
H
2
3
OH
H
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nucleoside
O
A nucleoside is the chemical combination of
base and sugar.
H3C
H
N
O
N
H
O
5
O
P
CH2
O-
O
O
1
4
O-
H
H
H
H
2
3
OH
H
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nucleotide
O
A nucleotide is the chemical combination of
base, sugar and phosphate.
H3C
H
N
O
N
H
O
5
O
P
CH2
O-
O
O
1
4
O-
H
H
H
H
2
3
OH
H
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5
O
The backbone of a nucleic acid is created by
connecting the phosphate of this monomer to the
3 position of another monomers
scaffolding sugar.
OH
O
1
4
H3C
H
H
H
N
H
H
3
2
H
OH
O
N
H
O
5
O
P
CH2
O-
O
O
1
4
O-
H
H
H
H
2
3
From 5C to 3C
OH
H
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3C
Nucleotides are added in the 5 to 3 direction
5C
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3-D
DNA in
Phosphate connectors, Right-hand strand 3 to 5
Phosphate connectors, Left-hand strand 5 to 3
Scaffolding Sugar Base nucleoside
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End of the Structure of Nucleic Acids and DNA
Beginning of DNA Replication
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DNA genes on chromosomes
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5 3
The DNA strand opens and will add nucleotides. G
to C and T to A.
One strand grows continuously, the other grows
discontinuously.
Enzymes join the strands.
5
3
5
3
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DNA Replication (inside the nucleus)
Parental DNA
DNA Helicase
Parental DNA with a replication fork
DNA Polymerase
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End of DNA Replication
Beginning of RNA Replication (Transcription)
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DNA produces Protein in two steps
Transcription mRNA production
Translation protein production
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Transcription of mRNA from DNA
Parental DNA
RNA Polymerase
Transcription mRNA Synthesis
Single stranded mRNA
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DNA
DNA coding sequence
RNA coding sequence
RNA
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INITATION of Transcription
GENE
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INITATION of Transcription
Elongation Phase
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INITATION of Transcription
Termination Phase
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INITATION of Transcription
Multiple mRNA Copies
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During Transcription mRNA code is produced from
DNA. GGG CCC TTT AAA
CCC GGG AAA UUU
What are the base code combinations?
To decode DNA into RNA use these base
combinations A-U, T-A, G-C, C-G Decode the DNA
sequence below into mRNA ATA TAT GCG GCC GAG
TCA TAA
UAU AUA CGC CGG CUC AGU AUU
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rRNA
Ribosomal RNA
5,080 RNA base (in 2 or 3 molecules) 49
embedded proteins
Eukaryotic Ribosome
1,900 RNA base (in a single molecule) 33
embedded proteins
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tRNA
Transfer RNA
Anticodon mRNA Binding Site
Amino Acid Accepting End
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End of mRNA Transcription
Beginning of Protein Synthesis (Translation)
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DNA produces Protein in two steps
Transcription mRNA production
Translation protein production
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From DNA to RNA to Protein
DNA coding sequence
RNA coding sequence
A- Inside the nucleus
mRNA
B- In the Cytosol
C- At to Ribosome
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Base Triplets form the Genetic Code
Triplets
The code words in DNA and RNA are composed of
three contiguous nucleotide bases called a
triplets or CODONs.
Original DNA Base Sequence
GACGACGACGACGAC
GUCGUCGUCGUCGUC
Translated mRNA Base Sequence
Remember! RNA substitutes U for T
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The DNA triplets which determine the mRNA codons
...
code for amino acids
at the ribosome...
during translation.
tRNA with and amino acid in tow
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tRNAs...

that matches the mRNAs codon.
have an anti-codon...
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Each of the 20 essential amino acids has its own
special tRNAs carriers.
mRNA
tRNA
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mRNA
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Translation mRNA tRNA
Protein
an mRNA arrives...
At the ribosome...
and tRNAs begin to bring their
amino acids...
tRNA
anti-codons match up with mRNA codons...
bonds form between
the amino acids.
UUU AAA CCC GGG CCC GGG AUU
UUU Lys
CCC Gly
UAA Ile
AAA Phe
GGG Pro
CCC Gly
GGG Pro
The tRNAs disengage
and the result is a pre-protein polypeptide
chain.
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Video
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End of Protein Synthesis (Translation)
Beginning of Extra Slides concerning DNA and RNA
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How is RNA different than DNA?

• Ribose Sugar
• Uracil for Thymine
• Single strand
• not self replicating
• found all over the cell

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• Nucleolus - Site of ribosome production
• Nucleus - location of DNA, cell organizer
• Chromosomes - coiled chromatin
• Chromatin - DNA and proteins not coiled
• DNA - helix shaped molecule with base sequences
  that make up the genetic code
• RNA - made by DNA, assists DNA to make proteins
  as a messenger (mRNA), transfer molecule (tRNA)
  and ribosomal RNA (rRNA).

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major groove
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minor groove
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DNA
DNA
protein
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differences between DNA and RNA
DNA RNA deoxyribonucleic acid
ribonucleic acid no hydroxyl on 2 sugar
hydroxyl on 2 sugar A, C, G, T A, C, G,
U thymine has methyl group (CH3) uracil has a
hydrogen atom at position 5 double
stranded single stranded or double
stranded synthesized in 5 -gt 3 direction
synthesized in 5 -gt 3 direction
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Information content of various organisms
Organism Millions of bp (base pairs) of DNA
Human (Homo sapiens) 3000 Yeast
(Saccharomyces cerevisiae) 12 Protist (Amoeba
dubia) 600000 Bacterium (Mycoplasma
genetalium) 0.5
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other biological uses for nucleotides/nucleosides
Intracellular communication cyclic adenosine
monophosphate (cAMP) is a common chemical
signalling molecule. Caffeine interferes with
cAMP signalling guanosine triphosphate (GTP)
and guanosine diphosphate (GDP) are used by a
class of signalling proteins in the cell. The
on/off switch is determined by what molecule is
bound Energy adenosine triphosphate (ATP) is
the energy currency of the cell energy is
stored in the covalent bonds which link the three
phosphates
NH2
N
NH2
O
N
H
N
N
H
N
N
caffeine mimics the effect of cAMP
H
N
O
N
CH2O
NH2
OH
O
P
O
O
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a nucleoside triphosphate is the used to build
up the polymer two phosphates are liberated
(pyrophosphate) when the next nucleotide is
added this chemical reaction is energetically
favorable
ATP (adenosine triphosphate)
remember, for DNA, dATP is used ATP is also the
energy molecule of the cell