8.3 DNA Replication
Review Questions:
1. What are the 3 phases of the cell cycle?
2. What phase do cells spend the most time?
3. What are the 3 stages of interphase?
4.
When in the cell cycle is DNA copied?
Review Questions:
1. DNA
WhatReplication
are the 3 phases of the cell cycle? Interphase,
8.3
mitosis, cytokinesis
2. What phase do cells spend the most time? Interphase
(normal growth and functions)
3. What are the 3 stages of interphase? Gap 1, Synthesis,
and Gap 2
When in the cell cycle is DNA copied?
Synthesis (S-phase)
4.
8.3 DNA Replication
KEY CONCEPT
DNA replication copies the genetic information of a cell.
EQ: How and where does DNA replication occur in
cells and the cell cycle? SB1.a, SB2.b
8.3 DNA Replication
Replication copies the genetic information.
• A single strand of DNA
serves as a template for a
new strand.
• The rules of base pairing
direct
replication.
• DNA is replicated during the
S (synthesis) stage of the
cell cycle.
• Each body cell (somatic
cell) gets a complete set of
identical DNA.
8.3 DNA Replication
Proteins carry out the process of replication.
• DNA serves only as a template.
• Enzymes and other proteins do the actual work of
replication.
– Enzymes (helicase) unzip the double helix.
– Free-floating nucleotides form hydrogen bonds
with the template strand.
nucleotide
The DNA molecule unzips
in both directions.
DNA Replication
polymerase enzymes bond the nucleotides together to
8.3–DNA
form the double helix.
– Polymerase enzymes form covalent bonds between
nucleotides in the new strand.
– So, DNA polymerase is responsible for adding
nucleotides to the exposed DNA template bases.
new strand
nucleotide
DNA polymerase
8.3 DNA Replication
• Two new molecules of DNA are formed, each with an
original strand and a newly formed strand.
• DNA replication is semiconservative.
original strand
Two molecules of DNA
new strand
8.3 DNA Replication
8.3 DNA Replication
Replication is fast and accurate.
• DNA replication starts at many points in eukaryotic
chromosomes.
There are many origins of replication in eukaryotic chromosomes.
• DNA polymerases can find and correct errors.
8.3 DNA Replication
Practice making complementary strands:
Write the complement for each of the following DNA
sequences…
1. ATT GCT CCG TTA
TAA
CGA
GGC AAT
2. CTC ATA TGC GGC
GAG TAT
ACG
CCG
General
replication is the process by which DNA
8.3 DNAdescription:
Replication
is copied during the cell cycle
PROCESS:
1. enzymes unzip (helicase) the double helix
in two directions at the same time
2. nucleotides pair with the exposed bases on
the template strands
3. DNA polymerase bonds the new
nucleotides together
END RESULT:
4. Two molecules of DNA identical to
the original molecule result; each
molecule contains one original strand
and one new strand
General
replication is the process by which DNA
8.3 DNAdescription:
Replication
is copied during the cell cycle
Identify the structures:
1. sugar-phosphate backbone
2. nitrogen-containing bases
3. DNA polymerase
4. newly synthesized strand of DNA