Structure & Function of
DNA
DNA Replication
Genetic Code & 3
Types of RNA
Transcription &
Translation
DNA &
Gene
Expression
DNA: DNA Replication
11/18/15
DNA REPLICATION
 Question 1
 How do organisms grow?
 Question 2
 What has to happen before a cell can divide?
 Question 3
 What will happen to the cells if DNA replication does not occur?
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DNA REPLICATION
DNA replication: the process of making a copy
of one strand of DNA
DNA replication has to occur before a cell can divide
DNA
Replication
DNA
Cell
Division
2. Four Nitrogen Bases found in
DNA
Adenine- A
Thymine- T
Guanine- G
Cytosine-C
3. Nitrogen bases pair up to keep the two strands of the
DNA molecule bonded together.
6.Process of DNA Replication
 A. Replication begins when the two strands of the DNA
molecule separate.
 B. Free nucleotides found floating
around in the nucleus attach to
the exposed nitrogen bases
according to the base pairing rules.
Watch Video on DNA Replication
Process of DNA Replication
 C. As a result a complementary strand forms
next to each original strand of DNA and two
identical DNA molecules form.
 8. Complementary- the manner in which the
nitrogenous bases of the DNA molecule align
(pair) with each other.
9. Enzymes are present during
replication that assist with each
step of the process.
DNA REPLICATION (write on the top
of page)
Replication
1. Enzyme DNA Helicase breaks the hydrogen bonds
between the bases
2. Nitrogen bases are exposed
HELICASE
DNA REPLICATION
Replication (cont.)
1. DNA Polymerase adds free nucleotides to the single
stranded DNA
2. DNA polymerase Proofreads the bases
DNA
Polymerase
Nucleotides
DNA REPLICATION
3,000 nucleotides/min
3.2 billion nucleotides in the human genome
 1,066,666 minutes to copy the human genome (2 years)
 Multiple replication forks speed up replication
Direction of replication
Direction of replication
Helicase
Replication
Forks
Helicase
DNA REPLICATION
 DNA replication is semiconservative
 Result is two new DNA strands (daughter strands). Each is
composed of 1/2 original strand and 1/2 new DNA
On your own:
 Where does DNA replication occur in a eukaryotic cell?
 What are the base-pairing rules for DNA?
 What would be the complementary strand for the DNA strand AT-T-C-G-G-A-T-C?
 How do the two new DNA molecules that result from DNA
replication compare with each other?
 How does each new DNA molecule that results from DNA
replication compare with the original DNA molecule?
 How are the nucleotides arranged in a DNA molecule?
On your own:
 Where does DNA replication occur in a eukaryotic cell?
 Nucleus
 What are the base-pairing rules for DNA?
 A-T, G-C
 What would be the complementary strand for the DNA strand A-T-TC-G-G-A-T-C?
 T-A-A-G-C-C-T-A-G
 How do the two new DNA molecules that result from DNA replication
compare with each other?
 Identical Copies
 How does each new DNA molecule that results from DNA replication
compare with the original DNA molecule?
 Complementary
 How are the nucleotides arranged in a DNA molecule?
 Stacked on top of one another