1. Introduction to
DNA &
RNA
Replication
Transcription
Translation

2. Why Did Caesar Die?
The Roman emperor Claudius Caesar (10 B.C.–
A.D. 54) had an appetite for the delicate taste
of mushrooms. Historians believe that
Caesar’s wife, Agrippina, wanted to poison
him. She mixed into Caesar’s favorite dish of
mushrooms a few of the poisonous species
Amanita caesarea. These poisonous mushrooms
contain a substance that blocks the activity of
an enzyme required for the cells to transcribe
messenger RNA from DNA.
For the first 10 hours after Caesar ate the
mushrooms, all seemed well as the
mushroom poisons entered the blood stream
and were absorbed by the liver and kidneys.
About 15 hours after eating the mushrooms,
Caesar’s liver cells stopped functioning.
Nausea, diarrhea, and delirium affected him
as his liver and kidneys could no longer filter
and detoxify wastes and other harmful
substances from the blood. He died two days
later from liver failure.

3. DNA (Deoxyribonucleic Acid)
 DNA holds the instructions for all cell
functions and all production of proteins
 Chromosomes are just tightly wound and
packaged strands (molecules) of DNA
 DNA is made up of repeating segments called
nucleotides

4. DNA Nucleotide
Nitrogenous bases:
Adenine
Guanine
Thymine
Cytosine
 Every living thing on
earth shares these
same 4 nucleotides

5. Nucleotide Sequence
 An elk, elm and eel all have the same four nucleotides
that make up their DNA
 Like the letters in their names, the order (or sequence)
of their nucleotides determine different traits that result
in very different organisms being produced

6. DNA Base-pairing
•DNA is made from 2 rows of side-by-side
nucleotides arranged in a specific order
• DNA has specific pairing between the bases:
 Guanine must pair with Cytosin
 Adenine must pair with Thymine

7. DNA Structure
P
G C
P T P
A
P C G P
H-bonds
P

8. DNA Double Helix
 Nitrogenous
bases form the
“rungs” of the
DNA “ladder”
1. Adenine (A)
2. Guanine (G)
3. Thymine (T)
4. Cytosine (C)

9. DNA Replication
 In order for cells to reproduce (make
more of themselves), DNA must be
copied
 Each of the 46 strands of the original
DNA serve as a template for new
copies
 A single strand of human DNA,
stretched out, would be about 6 feet
long, containing over 80 million base
pairs
 That’s about 46,000 books worth of information in 1 cell!
 With incredible accuracy, all of a cell’s DNA can be
replicated in about one hour

10. Replication
 First, DNA strands are
unwound and enzymes
“unzip” the molecule
 Next, new nucleotides are
added according to base
pairing rules
 This occurs simultaneously
at many different places
along a single strand of DNA
Parental DNA
New DNA
Templates

11. DNA Replication Video

12. REPLICATION: DNA is copied
 A codon is a 3-nuceotide segment which signals something
• Start and stop codons signal where replication can begin and end.

13. Think of it this way…
 Replication
• Making exact copies
• DNA  DNA
• Like a copy machine

14. DNA Replication Quiz
1. Why is replication necessary?
So both new cells will have the correct DNA
2. When does replication occur?
During Interphase (S phase). A---?
T
3. Describe how replication works. G---?
C
Enzymes unzip DNA and complementary C---?
G
nucleotides join each original strand. T---?
A
4. What happens to the original DNA? A---?
T
It serves as a template and half is incorporated G---?
C
into each of the two new strands.
A---?
T
5. Use the base pairing rule to T---?
A
create the complementary strand:

15. Transcription - portable copies
 During Interphase G1 or G0 (normal cell function),
DNA supplies the “codes” for proteins to be built
 DNA first must be transcribed into smaller
mRNA segments, serving as portable copies
 Why?
• Smaller segments are easier to move around
• Sending strands 80 million nucleotides long would be
inefficient (might be too long to find the “start”)
• It’s safer to send a copy than the original


16. RNA vs. DNA
 Ribose instead
of deoxyribose
 Uracil instead of
Thymine
 Shorter strands
 Single-stranded

17. TRANSCRIPTION: DNA to mRNA
 mRNA = “messenger” RNA
 DNA partially “unzips”
 mRNA nucleotides line up
on one side to form a
matching mRNA strand
 RNA retains DNA
sequences
• Uracil replaces Thymine
when matching with
Adenine
 mRNA takes the code to
ribosomes in the cytoplasm

18. Think of it this way…
 Transcription
• Same information, portable packaging
• DNA  RNA
• Like Bible-time scribes

19. Transcription Quiz
1. Why is transcription necessary?
Shorter mRNA strands are copied from DNA to
carry codes to ribosomes outside the nucleus.
A-- U
2. Describe transcription. C-- G
DNA strands separate, then one side is used as a
template to assemble mRNA nucleotides. C-- G
3. What are the main differences between G-- C
DNA and RNA. T-- A
RNA has ribose instead of deoxyribose; DNA has C-- G
2 strands while RNA has one; RNA has uracil
instead of thymine and RNA has shorter strands. A-- U
4. Use base pairing rules to create an C-- G
mRNA strand from this DNA template: G-- C

20. TRANSLATION: mRNA to Protein
 Messenger RNA carries the pieces of copied genetic
code out of the nucleus to a ribosome
 mRNA is “fed”
into the
ribosome
 Ribosome
helps tRNA
"read” the code
and assemble
a protein

21. Transfer RNA - tRNA
 tRNA = “transfer” RNA
 One tRNA molecule is composed
of ~ 80 nucleotides, three exposed
nitrogen bases (the anticodon)
and one amino acid
 tRNA anticodons match up with tRNA
mRNA codons inside a ribosome molecule
 As each tRNA molecule binds to
an mRNA codon, its amino acid is Amino
dropped off and linked together acids
 These assembled amino acid
chains (polypeptides) fold into
specific shapes to become new
proteins
anticodon
 The order of amino acids
determines what kind of protein
is made codon mRNA

22. mRNA Amino Acid “codes”
U C A G
UUU Phenylalanine UCU UAU Tyrosine UGU Cysteine U
UUC (Phe) UCC UAC (Tyr) UGC (Cys) C
Serine
U
UUA UCA (Ser) UAA Stop UGA Stop A
UUG UCG UAG Stop UGG Tryptophan (Trp) G
CUU Leucine CCU CAU Histidine CGU U
CUC (Leu) CCC CAC (His) CGC C
Proline Arginine
C
CUA CCA (Pro) CAA CGA (Arg) A
Glutamine
CUG CCG CAG (Gln) CGG G
AUU ACU AAU Asparagine AGU Serine U
Isoleucine (Asn) (Ser)
AUC ACC Threonine AAC AGC C
A (Ile)
AUA ACA (Thr) AAA AGA A
Lysine Arginine
AUG Methionine (Met) ACG AAG (Lys) AGG (Arg) G
GUU GCU GAU Aspartic Acid GGU U
GUC GCC GAC (Asp) GGC C
Valine Alanine Glycine
G
GUA (Val) GCA (Ala) GAA GGA (Gly) A
Glutamic Acid
GUG GCG GAG (Glu) GGG G

23. How Cells make Proteins
 mRNA copies small segments of DNA and carries
the code out of the nucleus to the ribosomes
 mRNA is fed through
ribosomes in cytoplasm
 tRNA match up with
mRNA codons (inside
ribosomes) and drop
off amino acids
 Ribosomes bond
amino acids together to
form proteins

24. Translation Quiz
1. Why is translation necessary?
It makes sure the right amino acids are joined together to
form the correct protein.
2. Describe translation.
Information from mRNA is used to produce proteins during
normal cell functions.
3. What are codons?
mRNA segments containing 3 nucleotides that code for a
specific amino acid.
4. Using a chart, identify the amino acids
coded for by this mRNA strand: UGG - tryptophan
CAG - glutamine
UGGCAGUGC UGC - cysteine

25. Think of it this way…
 Translation
• Information changes forms
• RNA  Protein
• Like translating English to French
or translating blueprints into a building

26. A helpful way to remember…
 Replication
• Making exact copies
• DNA  DNA
• Like a copy machine
 Transcription
• Same information, new packaging
• DNA  RNA
• Like sticky notes
 Translation
• Genetic info interpreted
• RNA  Protein
• Like translating English to French
or translating blueprints into a building