DNA, Replication and Protein Synthesis

1
DNA, Replication and Protein Synthesis
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
1953 - Watson and Crick Propose the structure of
DNA.
1951 - Paulings research on proteins gives
insight into the structure of DNA.
1952 Franklins work with X-ray diffraction
gives further clues as to the structure of DNA.
2
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 DNAs
double helix shape.
3
What Is The Structure of DNA?
Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Structure of Nucleotide
BASE
SUGAR (deoxyribose)
PHOSPHATE
P
P
P
P
4
What Is The Structure of DNA?
Sides of Ladder
Sides of Ladder
Rung
Cytosine ? Guanine
Rung
Adenine ? Thymine
Complimentary Pairs Are
Rung
C G A T
Rung
DNA Forms a Ladder Shape called a Double Helix.
5
The Life Cycle of the Cell
Nucleus
Transcription
Cell Growth and Everyday Activity Protein
Synthesis Transcription ? Translation
Interphase
Translation
RNA
Nucleus
Cytokinesis Cytoplasm is divided up into each
cell.
ReplicationDNA is doubled so each cell will have
an exact copy of DNA.
Replicated DNA is given to each cell.
Replication
Mitosis
6
26 letter AlphabetA 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 cells activities.
7
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.
8
This double helix structure makes it possible
for DNA to make an exact copy of itself.
1
DNA unzips itself.
2
Free-floating nucleotides attach themselves to
each side.
DNAPolymerase
This is known as replication.
9
MitosisDividing 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.
CytokinesisDividing of the cell
10
Cell DivisionThe newly formed cell receives the
replicated copy of DNA.
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.
Plant cell division
Animal cell division
11
Here is a practice website if you are connected
to the internet
http//www.pbs.org/wgbh/aso/tryit/dna/shockwave.ht
ml
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?
Blood cell with the correct DNA sequence for
shape.
Proteins are what make us different.
Blood cell with an incorrect DNA sequence for
shape.
But proteins also make sure that some things stay
the same.
13
DNA carries the genetic code, but it never leaves
the nucleus of the cell. So how does DNA direct
the activities from the nucleus?
The Answer Is RNA.
14
What is RNA?
I take the message from DNA to the ribosome.
1
Messenger RNA(mRNA)
2
Transfer RNA(tRNA)
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
15
What Is The Structure of RNA?
Purines
Pyrimidines
Adenine
Guanine
Cytosine
Uracil
Structure of Nucleotide
BASE
SUGAR (ribose)
PHOSPHATE
P
P
P
P
16
How does RNA differ from DNA?
DNA
RNA
1
Sugar
Ribose
Dexoyribose

• Sugar in RNA is ribose instead of deoxyribose.

Base
2

• The nitrogen base in RNA uracil replaces thymine.

Strands
3

• RNA is generally single stranded rather than
  double stranded.

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Protein Synthesis
1
Transcription
DNA makes messenger RNA (mRNA), and then it is
sent to the ribosome.
2
3
Translation
Protein Synthesis
mRNA serves as the code sotransfer RNA (tRNA)
can placethe amino acids in sequence.
The protein is made from the coded message.
ARG
LEU
LEU
ARG
MET
THR
THR
MET
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TranscriptionDNA writes its code to make mRNA.
Cytoplasm
Nucleus
Next is translation?
DNA
mRNA message sent to
Ribosome
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• 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.

20
Phenylal-anine
Glycine
GlutamicAcid
AsparticAcid
Leucine
U
G
C
A
A
C
G
U
U
G
G
A
U
C
C
A
A
U
C
G
Serine
Alanine
G
U
A
C
A
C
C
A
G
U
U
G
Tyrosine
G
U
G
U
A
C
Valine
Stop
A
C
G
U
Typtophan
G
U
A
C
G
U
Arginine
A
A
C
C
A
Leucine
C
U
G
Serine
G
U
A
C
A
C
C
A
Lysine
G
U
U
G
Proline
U
G
C
A
Asparagine
A
C
G
U
U
G
A
C
Histdine
A
C
G
U
Threonine
Glutamine
Methionine
Arginine
Isoleucine
This Is the start codon and begins the amino
acid chain.
21
TranslationThe ribosome and tRNA helps assemble
the protein chain of amino acids.
The amino acids are bonded together to start the
protein chain.
LEU
THR
MET
ARG
22
Mutations Mistakes In DNA
Correct Sequence
TAC
GCA
ATA
TGG
DNA
AUG
CGU
UAU
ACC
mRNA
MET
TYR
THR
ARG
THE
FAT
ATE
CAT
Point Mutation
Substitution
TAC
GTA
ATA
TGG
DNA
AUG
CAU
UAU
ACC
mRNA
MET
TYR
THR
HIS
THE
FTT
ATE
CAT
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Mutations Mistakes In DNA
Correct Sequence
TAC
GCA
ATA
TGG
DNA
AUG
CGU
UAU
ACC
mRNA
MET
TYR
THR
ARG
THE
FAT
ATE
CAT
Frameshift Mutations
Insertion
Deletion
Insertion of another G
Deletion of G
TAC
GGC
GAT A
ATG
DNA
TAC
CAT
TA
GGA
DNA
AUG
GUA
AU
CCU
mRNA
AUG
CCG
CUA U
UAC
mRNA
MET
TYR
TYR
PRO
MET
PRO
VAL
THE
FFA
TAT E
TCA
THE
ATC
TE
ATA
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The Life Cycle of the Cell
Nucleus
Transcription
Cell Growth and Everyday Activity Protein
Synthesis Transcription ? Translation
Interphase
Translation
RNA
Nucleus
Cytokinesis Cytoplasm is divided up into each
cell.
ReplicationDNA is doubled so each cell will have
an exact copy of DNA.
Replicated DNA is given to each cell.
Replication
Mitosis
25
Genes ? Proteins ? Traits
DNA Strand DNA Strand DNA Strand
Introns Does not code for protein
TATA Box Helps position RNA Polymerase close to
gene
1
3
5
RNAPolymerase
2
4
6
EnhancerAttracts RNA polymerase to this section
of DNA
ExonsCode for Protein
PromoterSequences
1
3
5
2
4
6
pre-mRNA
1
3
5
mRNA (after splice)
This allows millions of different possibilities
for proteins.
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Genes ? Proteins ? Traits
DNA Strand
TATA Box Helps position RNA Polymerase close to
gene
Introns
1
5
15
RNAPolymerase
2
4
6
Exons
1
5
15
2
4
6
pre-mRNA
1
5
15
mRNA (after splice)
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)
Similar. (same)
and
Blood cell with the correct DNA sequence for
shape.
Proteins are what make us different.
Blood cell with an incorrect DNA sequence for
shape.
But, proteins also make sure that some things
stay the same.
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