AP Bio Chapter 16
Figure 16.0 Watson and Crick
The Race for the Double Helix
• You’ve travelled back in time to the 1920’s!
• Since you’re so interested in learning about the
history of genetics, you’ve taken a job in Dr.
Frederick Griffith’s Laboratory
Figure 16.1 Transformation of bacteria
Race for the Double Helix
• Through studies of mice and bacteria, Frederick
Griffith concluded that _________________
________________________, but did not know
the cause.
• ________________, an American bacteriologist,
investigated this question.
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AP Bio Chapter 16
Race for the Double Helix
• Protein + bacteria
• Protein + bacteria -- > __________________
• Membrane + bacteria
Race for the Double Helix
• Avery’s results suggest that ______________
_______________________ .
• ____________________ experiment was used to
verify this conclusion.
• Membrane + bacteria -- > _____________
• DNA + bacteria
• DNA + bacteria -- > __________________
Figure 16.2a The Hershey-Chase experiment: phages
Figure 16.2ax Phages
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AP Bio Chapter 16
Figure 16.2b The Hershey-Chase experiment
Race for the Double Helix
• The supernatant contained radioactivity from the
protein coat. The pellet contained radioactivity
from the DNA.
• ________ discovered that DNA bases are present
in constant ratios in DNA molecules. _______are
present in equal amounts, and ________ are also.
• Although DNA varies from one species to
another, ________________________________.
Figure 16.4 Rosalind Franklin and her X-ray diffraction photo of DNA
Race for the Double Helix
• DNA must be it! The race is on!
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AP Bio Chapter 16
Figure 16.3 The structure of a DNA stand
Race for the Double Helix
• Watson and Crick were particularly perplexed by
the X-ray crystallography photo by _________
_______________. This photo allowed them to
deduce the structure of DNA in ___________.
Figure 16.0 Watson and Crick
DNA Structure
• ________________ with a ______________
backbone. Bases are the “rungs” of the ladder.
• ____________ – A and G (double-ring)
• ____________ – C and T (single ring)
• DNA replication is _______________________,
meaning:
• Each DNA strand is used as a template to make a new
strand
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AP Bio Chapter 16
Figure 16.5 The double helix
Unnumbered Figure (page 292) Purine and pyridimine
Figure 16.6 Base pairing in DNA
Figure 16.7 A model for DNA replication: the basic concept (Layer 4)
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AP Bio Chapter 16
Figure 16.8 Three alternative models of DNA replication
Figure 16.9 The Meselson-Stahl experiment tested three models of DNA replication (Layer 4)
DNA Replication Overview
• A conceptually simple process, but replication is:
1) ______________
•
DNA unwinds / copies simultaneously
•
Over a dozen molecules involved
2) ______________
•
3)
Takes _____________ to copy 6 billion bases of 1
human cell
The Major Players in Replication
1) _____________________________
• Unwinds the double helix at the origins of replication
2) _____________________________
•
Stabilize unwound DNA
3) ______________________________
•
First nucleotides added (about 10) are RNA bases.
Eventually replaced with DNA.
_____________
• _________________ errors
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AP Bio Chapter 16
Figure 16.10 Origins of replication in eukaryotes
The Major Players in Replication
4) ___________________
• Add DNA bases to the unwound strand. Can’t initiate
pairing. Replaces RNA bases with DNA.
5) ____________________
•
On the lagging strand, joins DNA fragments together
DNA is __________________; polymerase can add bases only
in the 5’ to 3’ direction.
The DNA fragments on the lagging strand are called
_______________fragments.
Figure 16.11 Incorporation of a nucleotide into a DNA strand
Figure 16.12 The two strands of DNA are antiparallel
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AP Bio Chapter 16
Figure 16.13 Synthesis of leading and lagging strands during DNA replication
Figure 16.14 Priming DNA synthesis with RNA
Figure 16.15 The main proteins of DNA replication and their functions
The Major Players in Replication
6) __________________ – Removes incorrectly paired-bases
from the DNA strand.
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AP Bio Chapter 16
Figure 16.16 A summary of DNA replication
Figure 16.17 Nucleotide excision repair of DNA damage
Figure 16.18 The end-replication problem
Replication and Aging
• Each time a eukaryotic chromosome is copied, it
_____________________! Bits of chromosome
are lost in each replication.
• Why? RNA primase at the start of the leading
strand can not be replaced with DNA bases!
• To avoid lost genetic info, chromosomes have a
non-coding region called the
__________________ at the end of them.
• This has interesting cloning implications …
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AP Bio Chapter 16
Figure 16.19a Telomeres and telomerase: Telomeres of mouse chromosomes
Figure 16.19b Telomeres and telomerase
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