Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 11
DNA: The Carrier of
Genetic Information
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• Evidence of DNA as hereditary
material
• Proteins—rather than nucleic acids—
thought to be genetic material in the
1930s and 1940s
• Several lines of evidence supported
DNA as genetic material
–DNA is transforming principle in bacteria
• Watson and Crick modeled DNA
structure
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Griffith’s transformation experiments
Established
that DNA
carries
necessary
information
for bacterial
transformation
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Hershey-Chase
experiments
Established that viral
DNA enters
bacterial cells
and is required for
synthesis of
new viral particles
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• Structure of DNA
• Regular polymer of nucleotides
–Nitrogenous base of purine or pyrimidine
–Base covalently links to deoxyribose
–Deoxyribose covalently bonds to a
phosphate group
• Backbone
–Alternating sugar and phosphate groups
joined by covalent phosphodiester linkages
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Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Nucleotide
subunits of DNA
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Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Base compositions in
DNA from selected
organisms
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• Structure of DNA molecule
• Two polynucleotide chains associated
as double helix
• Two chains are antiparallel (running in
opposite directions)
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
3-D model of
DNA
double helix
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• Base-pairing rules for DNA
• Hydrogen bonding between base pairs
holds together the two chains of helix
• Adenine (A) forms two hydrogen bonds
with thymine (T)
• Guanine (G) forms three hydrogen
bonds with cytosine (C)
• Chargaff’s rules
–A = T
–G = C
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Base pairing
and
hydrogen
bonding
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• DNA Replication
• Two strands of double helix unwind
• Each strand serves as template for new
strand
• DNA polymerase adds new nucleotide
subunits
• Additional enzymes and other proteins
required to unwind and stabilize DNA
helix
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Enzymes involved in
DNA replication
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Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Simplified view of DNA replication
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Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Overview of DNA replication
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Leading
and
lagging
DNA
strands
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• DNA replication
• Bidirectional, starting at origin of
replication
• Strands replicate at replication fork
• Two DNA polymerase molecules
catalyze replication
–Leading strand
–Lagging strand
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Bidirectional DNA replication in bacteria and
eukaryotes
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
• Replication at chromosome ends
• Telomeres
–Short, non-coding repetitive DNA sequences
–Shorten slightly with each cell cycles
–Can be extended by telomerase
–Absence of telomerase activity may be
cause of cell aging
• Most cancer cells have telomerase to
maintain telomere length and resist
apoptosis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 11 DNA: The Carrier of Genetic Information
Replication
at
chromosome
ends
Copyright © 2005 Brooks/Cole — Thomson Learning