Download DNA and RNA

1
DNA, Replication
and Protein Synthesis
1953 - WatsonWe
andwish to suggest a structure for the salt
Crick Propose ofthedeoxyribose nucleic acid (D.N.A.). This
structure has novel features which are of
structure of DNA.
considerable biological interest…
J. D. Watson
F. H. C. Crick
Nature (magazine) April 25, 1953
1952 – Franklin’s work with X-ray
diffraction gives further clues as to
the structure of DNA.
1951 - Pauling’s research on
proteins gives insight into the
structure of DNA.
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All the activities of the cell are controlled by DNA.
DNA is located in the nucleus of the cell.
Just before cell division DNA
coils to form chromosomes.
A Chromosome
is tightly coiled DNA.
When a chromosome is unraveled, it
reveals DNA’s double helix shape.
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What Is The Structure of DNA?
Purines
Adenine
Pyrimidines
Guanine Cytosine
Thymine
Structure of
Nucleotide:
BASE
SUGAR (deoxyribose)
PHOSPHATE
P
P
S
S
S
S
P
P
What Is The Structure of DNA?
S
S
P
P
S
P
S
S
P
A – T
S
C – G
T
G
Rung C
P
Complimentary
Pairs Are:
A
Rung
P
Adenine  Thymine
Sides of Ladder
S
Sides of Ladder
G
Rung
T
RungA
P
P
Cytosine  Guanine
C
S
4
DNA Forms a Ladder Shape
called a “Double Helix.”
5
The Life Cycle of
the Cell
DNA
Transcription
RNA
DNA
Cell Growth and
“Everyday Activity”
MET
~ Protein Synthesis ~
Transcription
LEU
Translation

RNA
Translation
Cytokinesis
Cytoplasm is
divided up into
each cell.
THR
ARG
T
A
T
AT
A
T
A
T
AT
A
C
G
C
CG
G
C
G
C
CG
G
G
A
G
Replication
C
GC
G
A
G
A
T
C
G
A
T
C
G
AT
C
T
GC
AT
GC
C
T
C
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26 letter Alphabet…
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Which is meaningless…
t e s a l R b h l a T d c a o g b g e l l n m s r o k o I c h d .
Unless…
Richard dog black The belongs to small.
The letters are put together in a meaningful way:
The small black dog belongs to Richard.
DNA works the same way.
DNA uses a four letter alphabet
to direct all of the cell’s activities.
The most important characteristic of DNA is the code
which occurs in complementary pairs
A, T, C and G. They are the 4 letter alphabet of the
genetic code which controls the activities of the cell.
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A
T
A
T
A
C
G
C
G
G
C
A
T
G
C
A
T
G
C
A
8
This “double helix structure” makes it possible
for DNA to make an exact copy of itself.
DNA “unzips itself.”
1
A
Free-floating
nucleotides attach
themselves to each
side.
2
This is known as
replication.
T
A T
A T
A
T
A T
A T
A
C
G C
G C
G
C
G C
G C
G
G
C G
C G
C
A
T A
T A
T
G
C G
C G
C
A
T A
A
C G
C G
G
DNA T
Polymerase
T
C
A
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Mitosis:
Dividing the DNA
When cells divide, they must make a copy
of the DNA so the two resulting cells each
have the exact same copy of genetic code.
Cytokinesis:
Dividing of the cell
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Cell Division
The newly formed cell receives
the replicated copy of DNA.
T
A T
A T
A
T
A T
A T
A
C
G C
G C
G
C
G C
G C
G
G
C G
C G
C
A
T A
T A
T
G
C G
C G
C
A
T A
T A
T
G
C G
C G
C
The free-floating nucleotides in the nucleus attach
themselves to each side of the ladder.
Once
replication
has occurred,
the cell can now divide into two.
Animal cell division:
Plant cell division:
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Here is a practice website if you are connected to the internet:
http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html
12
Cells must make a copy of DNA (replication)
before the cell divides so that each cell has a
copy of the genetic code.
Question: What is the genetic code used for?
Answer: making proteins
Why are proteins important?
Proteins are
what make us
different.
Blood cell with
the correct DNA
sequence for
shape.
But proteins also
make sure that
some things stay
the same.
Blood cell with an
incorrect DNA
sequence for
shape.
DNA carries the genetic
code, but it never leaves the
nucleus of the cell.
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So how does DNA direct the
activities from the nucleus?
The Answer Is… RNA.
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What is RNA?
Messenger RNA
(mRNA)
1
2
I take the message
from DNA to the
ribosome.
Transfer RNA
(tRNA)
LEU
mRNA tells us the order
of the amino acids in
making proteins.
3
Ribosomal RNA
(rRNA)
We stay in the ribosome and help
with the bonding of amino acids.
Ribosome
rRNA
15
What Is The Structure of RNA?
Purines
Adenine
Pyrimidines
Guanine Cytosine
Uracil
Structure of
Nucleotide:
BASE
SUGAR (ribose)
PHOSPHATE
P
P
S
S
S
S
P
P
How does RNA differ from DNA?
16
1
Ribose
Dexoyribose
Sugar in RNA is ribose instead of deoxyribose.
2
The nitrogen base in RNA uracil replaces thymine.
A
A
T
G
T
C
G
C
C
G
C
T
G
T
A
A
G
C
3
RNA is generally single stranded rather than double stranded.
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Protein Synthesis
1
Cell Growth
Protein Synthesis:
Transcription

Transcription
Translation
DNA makes messenger RNA (mRNA),
and then it is sent to the ribosome.
2
Translation
3
mRNA serves as the code so
transfer RNA (tRNA) can place
the amino acids in sequence.
Protein Synthesis
The protein is made
from the coded message.
LEU
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Transcription
DNA writes its code to make mRNA.
Next is translation
DNA
T
T
RNA
T
T
T
T
T
T
T
T
T
T
T
T
DNA
19 The genetic code is built into triplets of

nucleotides. (i.e. UGC)
 These sequences code for specific amino acids.
(i.e. UGC codes for serine)
 mRNA triplet code is called a codon.
(i.e. UGC on mRNA)
 tRNA triplet code is called an anti-codon.
(i.e. ACG on mRNA)
 The circle chart refers to the codon to identify
the amino acid. (i.e. UGC codes for serine)
 In this next activity you will learn this
“secret code” and make proteins.
VAL
anticodon
mRNA Codon
Arginine
C
U
G
A
U
G
A
C
U
G
A
C
U
G
A
C
tRNA
MET
anticodon
mRNA Codon
C
This Is the “start”
codon and begins the
amino acid chain.
U
G
A
C
AG UC
A
G
U
C
A
G
A
G U G
U
A C C
C UG A
U
U
GA C
U GA C
G
AC
U
anticodon
U
C
A Stop
G Typtophan mRNA Codon
U
A
PRO
C
G
U
C
A
G
tRNA
G
A
C
U
A G U C AG
U C
U
AG
C
tRNA
LEU
tRNA
20
anticodon
mRNA Codon
21
Translation
Cell Growth
Protein Synthesis:
Transcription
The ribosome and tRNA helps assemble
the protein chain of amino acids.

Translation
The amino acids are bonded
together to start the protein chain.
MET
ARG
THR
LEU
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Mutations – Mistakes In DNA
Correct Sequence:
DNA TAC
mRNA AUG
GCA
CGU
TGG
ACC
ATA
UAU
MET
ARG
THR
TYR
THE
FAT
CAT
ATE
Point Mutation
Substitution
DNA TAC
mRNA AUG
GTA
CAU
TGG
ACC
ATA
UAU
MET
HIS
THR
TYR
THE
FTT
CAT
ATE
Mutations – Mistakes In DNA
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Correct Sequence:
DNA TAC
mRNA AUG
GCA
CGU
TGG
ACC
ATA
UAU
MET
ARG
THR
TYR
THE
FAT
CAT
ATE
Frameshift Mutations
Insertion
Deletion
Insertion of another “G”
DNA TAC
mRNA AUG
GGC
CCG
ATG
UAC
GAT A
CUA U
MET
PRO
TYR
TYR
THE
FFA
TCA
TAT E
Deletion of “G”
DNA TAC
mRNA AUG
CAT
GUA
GGA
CCU
MET
VAL
PRO
THE
ATC
ATA
TA
AU
TE
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The Life Cycle of
the Cell
DNA
Transcription
RNA
DNA
Cell Growth and
“Everyday Activity”
MET
~ Protein Synthesis ~
Transcription
LEU
Translation

RNA
Translation
Cytokinesis
Cytoplasm is
divided up into
each cell.
THR
ARG
T
A
T
AT
A
T
A
T
AT
A
C
G
C
CG
G
C
G
C
CG
G
G
A
G
Replication
C
GC
G
A
G
A
T
C
G
A
T
C
G
AT
C
T
GC
AT
GC
C
T
C
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Genes  Proteins  Traits
Introns
TATA Box
Does not code for protein
Helps position RNA
Polymerase close to gene
RNA
Polymerase
1
3
4Strand
5
6
DNA Strand – DNA Strand
–2 DNA
Enhancer
Attracts RNA polymerase
to this section of DNA
Promoter
Exons
Sequences
pre-mRNA
mRNA (after splice)
This allows millions of different
possibilities for proteins.
Code for Protein
1
2
1
3
3
Protein-a
4
5
5
6
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Genes  Proteins  Traits
TATA Box
Introns
Helps position RNA
Polymerase close to gene
1
2
5Strand
4 15
DNA
6
RNA
Polymerase
Exons
pre-mRNA
mRNA (after splice)
1
2
1
5
5
4
15
15
6
Protein-b
Exons 1 & 5 in this gene are used to make a different protein.
Think of the variety of proteins that can be
coded using different combinations of exons!!!
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Remember:
It is our proteins that make us…
Unique
(different)
and Similar.
Proteins are
what make us
different.
(same)
Blood cell with
the correct DNA
sequence for
shape.
But, proteins also
make sure that
some things stay
the same.
Blood cell with an
incorrect DNA
sequence for
shape.
28
DNA  Proteins  What We Are
We wish to suggest a structure for the salt
of deoxyribose nucleic acid (D.N.A.). This
structure has novel features which are of
considerable biological interest…
J. D. Watson
F. H. C. Crick
Nature (magazine) April 25, 1953