1. DNA, Replication and Protein Synthesis
Watson and Crick Propose the structure of DNA.
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
1952 – Franklin’s work with X-ray diffraction gives further clues as to the structure of DNA.
Pauling’s research on proteins gives insight into 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 DNA’s double helix shape.

3. What Is The Structure of DNA?
Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Structure of Nucleotide:
BASE
SUGAR (deoxyribose) S S S S
PHOSPHATE P P P P

4. What Is The Structure of DNA?
Sides of Ladder
Sides of Ladder P S C P S G
Rung
Cytosine  Guanine P S A P S T
Rung
Adenine  Thymine P S G P S C
Complimentary Pairs Are:
Rung
C – G
A – T P S T P S A
Rung
DNA Forms a Ladder Shape called a “Double Helix.”

5. The Life Cycle of the Cell
Nucleus
DNA
Transcription
RNA
DNA
Cell Growth and “Everyday Activity” ~ Protein Synthesis ~ Transcription 
Translation
Interphase
MET
ARG
THR
LEU
Translation
RNA
Nucleus
Cytokinesis Cytoplasm is divided up into each cell.
Replication DNA is doubled so each cell will have an exact copy of DNA. T C G A A T A C G T A T C G
“Replicated DNA” is given to each cell. A T G C G
Replication C
Mitosis C G T A C G T A C G

6. The letters are put together in a meaningful way:
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. T C A G

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. T T A T T T A T G C G C C G G G C A A A T C G C A C T G A A G C

8. Free-floating nucleotides attach themselves to each side.
This “double helix structure” makes it possible for DNA to make an exact copy of itself. 1
DNA “unzips itself.” T G A T C G A A T T A C G A T C G T A T G G G C T A C G C C C G 2
Free-floating nucleotides attach themselves to each side. C T A A C G T T A
DNA Polymerase
This is known as
replication. A C G

9. 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

10. Cell Division The newly formed cell receives the replicated copy of DNA.G A A T T A C G A T C G A T G C
The free-floating nucleotides in the nucleus attach themselves to each side of the ladder. G C
Once replication has occurred, C G
the cell can now divide into two. T A
Animal cell division:
Plant cell division: C G T A C G

11. Here is a practice website if you are connected to the internet:

12. Why are proteins important?
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. So how does DNA direct the activities from the nucleus?
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? Messenger RNA (mRNA) 1 Transfer RNA (tRNA) 2 3
I take the message from DNA to the ribosome. 2
Transfer RNA (tRNA)
LEU
MET
ARG
THR
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
Pyrimidines
Adenine
Guanine
Cytosine
Uracil
Structure of Nucleotide:
BASE
SUGAR (ribose) S S S S
PHOSPHATE P P P P

16. How does RNA differ from DNA?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.

17. Cell Growth Protein Synthesis: Transcription
Replication
Cell Growth Protein Synthesis: Transcription 
Translation
Interphase
Mitosis
Cell Division
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 so transfer RNA (tRNA) can place the amino acids in sequence.
The protein is made from the coded message.
LEU
ARG
LEU
MET
ARG
THR
THR
MET

18. Transcription DNA writes its code to make mRNA.
Cytoplasm
Transcription DNA writes its code to make mRNA.
Nucleus
Next is translation T
DNA
RNA
RNA T
DNA
mRNA message sent to T
DNA
Ribosome

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.

20. This Is the “start” codon and begins the amino acid chain.
anticodon
tRNA
VAL
anticodon
tRNA
LEU
Phenylal- anine
Glutamic Acid
Glycine
Aspartic Acid
Leucine A G U C C A U G G U A G U C C A A U C G
Serine
Alanine G U A C C A C A U G G U
Tyrosine
mRNA Codon G U G U
mRNA Codon
Valine A C C A
Stop U G
Typtophan G A C U G U
anticodon
tRNA
MET
Arginine A A
anticodon
tRNA
PRO C A C
Leucine U C G
Serine G U A C A C
Lysine C U G A U G
Proline G U
Asparagine A C C A U G G C U A C
Histdine U G A
Threonine
Glutamine
Methionine
Isoleucine
Arginine
mRNA Codon
mRNA Codon
This Is the “start” codon and begins the amino acid chain.

21. Cell Growth Protein Synthesis: Transcription
Replication
Cell Growth Protein Synthesis: Transcription 
Translation
Interphase
Mitosis
Cell Division
Translation The ribosome and tRNA helps assemble the protein chain of amino acids.
The amino acids are bonded together to start the protein chain.
MET
ARG
THR
LEU

22. Mutations – Mistakes In DNA
Correct Sequence:
DNA
TAC
GCA
TGG
ATA
mRNA
AUG
CGU
ACC
UAU
MET
ARG
THR
TYR
THE
FAT
CAT
ATE
Point Mutation
Substitution
DNA
TAC
GTA
TGG
ATA
mRNA
AUG
CAU
ACC
UAU
MET
HIS
THR
TYR
THE
FTT
CAT
ATE

23. Mutations – Mistakes In DNA
Correct Sequence:
DNA
TAC
GCA
TGG
ATA
mRNA
AUG
CGU
ACC
UAU
MET
ARG
THR
TYR
THE
FAT
CAT
ATE
Frameshift Mutations
Insertion
Deletion
Insertion of another “G”
Deletion of “G”
DNA
TAC
GGC
ATG
GAT A
DNA
TAC
CAT
GGA TA
mRNA
AUG
CCG
UAC
CUA U
mRNA
AUG
GUA
CCU AU
MET
PRO
TYR
TYR
MET
VAL
PRO
THE
FFA
TCA
TAT E
THE
ATC
ATA TE

24. The Life Cycle of the Cell
Nucleus
DNA
Transcription
RNA
DNA
Cell Growth and “Everyday Activity” ~ Protein Synthesis ~ Transcription 
Translation
Interphase
MET
ARG
THR
LEU
Translation
RNA
Nucleus
Cytokinesis Cytoplasm is divided up into each cell.
Replication DNA is doubled so each cell will have an exact copy of DNA. T C G A A T A C G T A T C G
“Replicated DNA” is given to each cell. A T G C G
Replication C
Mitosis C G T A C G T A C G

25. Genes  Proteins  Traits
DNA Strand – DNA Strand – DNA Strand
Genes  Proteins  Traits
TATA Box
Helps position RNA Polymerase close to gene
Introns
Does not code for protein 1 3 5
RNA Polymerase 2 4 6
Enhancer Attracts RNA polymerase to this section of DNA
Promoter Sequences
Exons Code for Protein 1 3 5 2 4 6
pre-mRNA 1 3 5
mRNA (after splice)
Protein-a
This allows millions of different possibilities for proteins.

26. Genes  Proteins  Traits
DNA Strand
TATA Box
Helps position RNA Polymerase close to gene
Introns 1 5 15
RNA Polymerase 2 4 6
Exons 1 5 15 2 4 6
pre-mRNA
Protein-b 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!!!

27. Unique and Similar. Remember: It is our proteins that make us…
(different)
and
Similar.
(same)
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