Download CH 14 DNA Replication

CH 14 DNA Replication
Outline
• Chemical Nature of Nucleic Acids
• Three-Dimensional Structure of DNA
– Watson and Crick
• Replication
– Semi Conservative
– Replication Process
• One-Gene/One-Polypeptide Hypothesis
DNA is the Genetic Material
The Dawn of Molecular Biology
April 25, 1953
Chemical Nature of Nucleic Acids
•
DNA made up of ____________________
– Each nucleotide is composed of a ________________________________________
_______________________________.

nucleotides distinguished by the __________
– reaction between phosphate group of one nucleotide and hydroxyl group of another is
_______________________
 phosphodiester bond
Chemical Nature of Nucleic Acids
• Purines - large bases
– adenine and guanine
• Pyrimidines - small bases
– cytosine and thymine
 Chargaff’s rule
– A = T and G = C
•


__________________________ suggested DNA had helical shape with a 2 nanometer diameter.
– Watson and Crick deduced DNA is an ___________________________________.
complementary base-pairing
– ___________________________________
– constant 2 nanometer diameter
____________________ configuration
Models for DNA replication
1) Semiconservative model: _____________________________________________________
______________________________________________
2) Conservative model:
________________________________________________________________________________
__________________________________________________
3) Dispersive model:
________________________________________________________________________________
________________________________________________________
DNA Replication
• Since DNA replication is ______________________, therefore the helix must be
__________________.
•
Replication as a process
•
Double-stranded ___________________.
The junction of the unwound molecules is
a __________________________
A new strand is formed by ________________
_______________________________________.
Two molecules are made. Each has one new
and one old DNA strand.
Semi-Conservative Replication
• Each chain in the helix is a ___________________________________ of the other.
– double helix unzips and undergoes _________________________________
• each strand original duplex becomes one strand of another duplex
– confirmed by ________________________________- experiment
Replication Process
• Replication of DNA begins at one or ___________________________________.
• DNA polymerase III and other enzymes add nucleotides to the growing
complementary DNA strands.
– require a primer
• can only synthesize in ______________________
– endonucleases
– exonucleases
Replication Process
• DNA polymerase cannot link the _______________________ in a newly
synthesized strand.
– RNA polymerase (primase) constructs an ___________________.
• DNA polymerase adds nucleotides to ___________________.
– Leading strand replicates ______________ replication fork.
– Lagging strand elongates ______________ replication fork.
 Okazaki fragments
Replication Process
• ______________________ attaches fragment to lagging strand.
– Because synthesis of the leading strand is continuous and the lagging
strand is ____________________________, the overall replication of DNA
is referred to as __________________.
• ________________ removes torsional strain introduced by opening double helix
• Opening DNA double helix
– initiating replication
– unwinding duplex
– stabilizing single strands
– relieving torque
• Building a primer
• Assembling complementary strands
• Removing the primer
• Joining Okazaki fragments
Overview - Features of DNA Replication
• DNA replication is ____________________
– Each strand of both ________________ is being copied.
• DNA replication is _______________________
– Bidirectional replication involves two replication forks, which move in
opposite directions