Download DNA replication - Olympic High School

Our Guiding Question
• WHAT DETERMINES THE ORDER OF
AMINO ACIDS IN A PROTEIN???
Warm-up
1. Which parts of the nucleotides are
connected to make one strand (half) of
DNA?
2. Which parts of the nucleotides connect
the two strands (halves) of DNA?
3. What type of bond connects the two
strands together?
4. If a DNA molecule is 30%Adenine how
much Cytosine is there?
What does DNA look like?
• We can describe its molecular structure
• We can say what DNA looks like after
isolation.
How is DNA made?
DNA replication
DNA Replication
Whenever a cell divides into two new cells, it
needs to make an exact copy of the DNA.
What would happen if a cell divided without
DNA making a copy of itself?
The process of copying DNA is called DNA
replication.
Enzymes in DNA replication
• Enzymes are proteins that act as machines
in the cell to do work.
• 2 enzymes do the work of DNA replication:
– Helicase is responsible for separating the
2 strands of DNA
– DNA Polymerase is responsible for
adding on new Nucleotides.
We will replicate (copy) our DNA molecule in class to
produce 2 new identical DNA molecules
Helicase
• Helicase unwinds and separates the 2 strands of DNA so
that each strand may be copied.
• Helicase breaks the hydrogen bonds between the bases
of each strand.
Hydrogen
Bonds
DNA Polymerase
•
•
DNA Polymerase
adds on the
complimentary
bases to the new
strands of DNA
DNA Polymerase
makes bonds
between the
phosphate and the
deoxyribose sugar
of the nucleotides.
DNA Polymerase
Complementary base pairing
• If one strand of DNA has the following
sequence,
CTAATGT
GATTACA
What is the base sequence (order of
nucleotides) for the complimentary
strand?
Complicated picture of replication…
Replication in Action
• Replication occurs simultaneously at
multiple places along a DNA strand.
– 1 chromosome is about 80 million base pairs
long.
– Replication is as fast as 50 base pairs a
second!
Flash Animation:
http://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swf