Download DNA Structure

The Molecule of Life
What are the different DNA Nitrogen
Bases
1.Purines – double ring structure.
Adenine
Guanine
2.Pyrimidines – single ring structures
Cytosine
Thymine
DNA Structure

The DNA
structure is shaped
like a spiral stair
case:
Double helix
DNA REPLICATION
Replication
is the process
where DNA
makes an
exact copy of
itself.
If you were to replicate
DNA why would you do it,
and how would you do it?
JQ: Your pet dog
stepped on a
sharp rock and
got a cut. Be as
detailed as you
can in explaining
what happens next
in the area of the
wound.
Need your
textbooks!
DNA REPLICATION
Dispersive Replication
DNA REPLICATION
Conservative Replication
DNA REPLICATION
Semi-Conservative Replication
DNA REPLICATION
Meselson & Stahl
Create the Most
Beautiful Experiment
in Molecular Biology
What do the results tell us?
Hypothesis: Semi-Conservative
What do the results tell us?
General Ovewrview for DNA Replication
1. The two DNA strands separate (dark
blue)
2. Each open strand serves as a template
for the new strand (light blue)
3. Complimentary bases are added.
How is this all possible? What is doing
the work?
What are the steps of
DNA REPLICATION
What can you tell me/
What do you notice about
this DNA?
Strands run in opposite
Directions - they are
Antiparallel
5’ (five prime) end - has
Phosphate on end
3’ (three prime) end - has
Hydroxyl group attached
Replication in Real Time
Replication Broken Down
DNA REPLICATION
1. DNA Helicase (enzyme) splits open
double strand at origin and unwinds
DNA. SSB’s keep the strand open.
2. RNA primase gets strand ready for
DNA Polymerase (enzyme) to
attaches free floating nucleotides in a
5’ to 3’ position on both strands.
Stands are copied in one direction.
DNA REPLICATION
Leading Strand – is copied in one
direction continuously.
Lagging Strand –is looped around and
copied in fragments (okazaki fragments).
Okazaki fragments are linked together
by an enzyme called ligase.
DNA Replication Stats
• 1 strand of DNA ~ 150,000,000 base pairs
• 50 base pairs copied per second
• 834 molecules working at the same time!
• Humans have 46
pieces of DNA in
their cells.
What’s the next question
biologists asked?
Protein Synthesis
Process of making proteins
Players Involved
1. mRNA – messenger RNA,
reads message from DNA
2. tRNA – transfer RNA, transfers amino
acids
3. rRNA – ribosomal RNA, joined with
proteins to make up the ribosome
(protein factory of the cell)
Many, many, many enzymes are
involved in this process as well.
Nucleic Acids - RNA

Monomer Unit – Nucleotide

Ribose Sugar
Phosphate Group
 Nitrogen Base

P
Sugar
N. Base
RNA Nitrogen Bases
1.Purines – double ring structure.
Adenine
Guanine
RNA Nitrogen Bases
2.Pyrimidines – single ring structures
Cytosine
Uracil
RNA Structure

The RNA is single
stranded
Protein Synthesis Stages


Transcription – the process of obtaining
info. from the DNA on how to make the
protein. DNA
mRNA
Translation – the process of using the
information (mRNA) to construct the
protein.
Protein Synthesis Transcription
Why do fireflies glow?
Protein Synthesis Translation
Now that we know how
protein synthesis works,
what is the next question?
How is it controlled?
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