DNA
“The Molecule of Life”
Do Now
 What is DNA?
 Why is it important?
 Who helped to discover DNA and it’s
structure?
 Draw a picture of what you think DNA looks
like.
Objectives
 To explain the structure of DNA
 To identify the different types of bases and
which pair with which.
 To list the scientists involved in discovering
DNA.
DNA
 What do the letters stand for?

DEOXYRIBONUCLEIC ACID
 Where is it found?

In the nucleus (or nuclear region in
prokaryotes)
 What is it used for?

Blueprints of your genes/traits
What is DNA Made of?
 Repeating units of nucleotides
DNA STRUCTURE
 Nucleotides:



5 carbon sugar (Deoxyribose)
Phosphate Group
Nitrogen base
Nitrogenous Bases
 Purines


Double ring structure
*Adenine and Guanine
 Pyrimidines


Single ring structure
* Thymine, Cytosine, Uracil
Nitrogenous Bases
Erwin Chargaff
 Chargaff’s rule


C= G
T=A
Draw in the complimentary sequence
ATGCTAATTCGCATCG
Rosiland Franklin
 X-ray Diffraction use of
photo 51
 X-ray diffraction data
helped solve the structure
of DNA
 Indicated that DNA was a
double helix
X-Ray Crystallography
Watson and Crick
 Built a model of the double helix that
conformed to the others’ research



two outside strands consist of alternating
sugar and phosphate molecules
cytosine and guanine bases pair to each other
by three hydrogen bonds
thymine and adenine bases pair to each
other by two hydrogen bonds
DNA Structure
 DNA often is compared to a
twisted ladder.
 Rails of the ladder are
represented by the alternating
deoxyribose and phosphate.
 The pairs of bases (cytosine–
guanine or thymine–adenine)
form the steps.
Label the parts of the DNA molecule
Structure Worksheet!
Do Now
 How does DNA get into EVERY cell of our
bodies?
 Is it the same in every cell?
 What is RNA?
 How is it different from DNA?
Objectives
 To understand how DNA is replicated.
 To compare and contrast DNA vs. RNA.
DNA Replication
 Allows cells to get an exact copy of DNA.
Steps to Replication
 1- The two DNA strands unwind and
separate.
Steps to Replication
2- Nucleotides in the area around the DNA
match up base by base with the nucleotides
on each TEMPLATE DNA strand.

All of the C’s pair with the G’s and all of the A’s
pair with the T’s.
Steps to Replication
 3- Each new molecule has one strand of new
DNA and one from the original strand.
Replication Animation
 http://www.johnkyrk.com/DNAreplication.html
What is DNA responsible for again?
RNA is needed to make proteins!
 What is RNA?

Ribonucleic Acid
 How is it different from DNA?




Single Stranded
Indefinite shape
Uses “uracil”
Contains Ribose
Types of RNA
 Messenger RNA (mRNA)


Located in both the nucleus and the cytoplasm
Brings genetic code from DNA to the ribosome
to make protein
Types of RNA
 Ribosomal (rRNA)


Located within the ribosome
Helps make the structure of the ribosome
Types of RNA
 Transfer (tRNA)


Located in the cytoplasm
Brings amino acids to ribosome to build
proteins.
DNARNAProtein
 Transcription:


Occurs in nucleus
Create mRNA from DNA
 Translation:


Occurs in cytoplasm
Takes mRNA and makes proteins with the help
of tRNA.
DNA vs. RNA worksheet!
Do Now
 What are the 3 types of RNA?
 What is the purpose of each of them?
 What are the names of the two processes
involved in making proteins?
Objectives
 To understand how mRNA is made.
 To determine how proteins are made through
the process of translation.
Transcription
** Only individual genes are transcribed, not a
whole DNA molecule.
What is the first step to making a protein?
Transcription
 Step 1: DNA molecule unwinds and
separates just like in replication.
Transcription
 Step 2: RNA nucleotides match up with their
complimentary bases on the template strand.
 Practice: Write the complimentary mRNA
strand from this DNA…

ATCGATGGCAAGCTA
Transcription
 Step 3: mRNA detaches once entire gene is
done and the DNA recoils.
 *Many copies of RNA can be made from the
same gene in a short period of time.
Translation
 What happens in translation?
 Where does this happen?
Translation
 Step 1: Translation begins when a ribosome
attaches to the beginning end of an mRNA
molecule.
 *Translation MUST START AT THE LETTERS
“AUG”.
 * Every 3 letters on the mRNA is called a
“Codon” that codes for a specific amino acid.
CODON BINGO!!
Translation
 Step 2: A tRNA molecule carrying an amino
acid matches up to a complementary codon
in the mRNA on the ribosome.
 *tRNA molecules contain “Anticodons”
which are 3 bases on the tRNA.
Translation
 Step 3: The ribosome attaches one amino
acid to another as it moves along the mRNA
molecule.

Amino acids are attached by PEPTIDE
BONDS.
Translation
 Step 4: The tRNA molecules are released
after the amino acids they carry are attached
to the growing chain of amino acids.
Translation
 Step 5: The ribosome completes the
translation when it reaches a stop codon. The
newly made protein molecules in the form of
a chain of amino acids, is released.
Practice!
 Translate this mRNA sequence.
 *Remember to start and stop at the right
places!!
TCACTAUGCGGACGGACATTATCG
Translation Practice
Worksheet!