PowerPoint Notes on Chapter 9 - DNA: The Genetic Material 9 Studen… · PowerPoint Notes on...
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PowerPoint Notes on Chapter 9 - DNA: The Genetic Ma terial
Griffith’s Discovery of Transformation
Section 2 The Structure of DNA
Objectives • Describe the three components of a nucleotide. • Develop a model of the structure of a DNA molecule. • Evaluate the contributions of Chargaff, Franklin, and Wilkins in helping Watson and Crick
determine the double-helical structure of DNA. • Relate the role of the base-pairing rules to the structure of DNA.
DNA Overview (Video clip)
DNA is made up of subunits called ____________________, each made of 3 parts: a _______,
a ______________ group, and a ______________base. In DNA, the sugar is _____________.
A Winding Staircase • Watson and Crick determined that a DNA molecule is a ____________________ — two
strands twisted around each other, like a winding staircase.
• _______________________ are the subunits that make up DNA. Each nucleotide is
made of three parts: a phosphate group, a five-carbon sugar molecule, and a nitrogen-
containing base.
• ______________________________________________________________________.
Double Helix (Video clip) To what do they compare DNA’s double helix? ______________
Nucleotides (Video clip) What portion of the ladder do the sugars and phosphate groups of
a nucleotide form? ____________ The nitrogen bases face each other and bond to form
what portion of the ladder? __________________
• The nitrogen base in a nucleotide can be either a bulky, _________________________,
or a smaller, _______________________________.
Structure of a Nucleotide Discovering DNA’s Structure:
Chargaff’s Observations • In 1949, Erwin Chargaff observed that for each organism he studied, _______________
______________________________________________________________________
• Likewise, ______________________________________________________________
• However, the amount of adenine and thymine and of guanine and cytosine __________
_______________________________________
Wilkins and Franklin’s Photographs • By analyzing the complex patterns on X-ray diffraction photo, scientists can determine
____________________________________________.
• In 1952, Maurice Wilkins and Rosalind Franklin developed high-quality X-ray diffraction
photographs of _____________________________.
• These photographs suggested that the DNA molecule ___________________________
______________________________________________________________________
Watson and Crick’s DNA Model • In 1953, _______________________________________________________________,
a “spiral staircase” of two strands of nucleotides twisting around a central axis.
• The double-helical model of DNA takes into account ____________________________
______________________________________________________________________
Pairing Between Bases • An adenine on one strand always pairs with a _______________ on the opposite strand,
and a guanine on one strand always pairs with a ____________ on the opposite strand.
• These __________________________ are supported by _____________ observations.
• The strictness of base-pairing results in ______________________________________
___________________________________________________
• The diagram of DNA below the helix makes it easier to visualize the base-pairing that
occurs between DNA strands.
(Video clip) Complementary Base Pairing What are the base pairing rules? ______________
____________________________________________________________________________
Section 3 The Replication of DNA Objectives
• Summarize the process of DNA replication. • Describe how errors are corrected during DNA replication. • Compare the number of replication forks in prokaryotic and eukaryotic DNA.
Roles of Enzymes in DNA Replication
• The complementary structure of DNA is used as a basis to ______________________
_________________________________________________
• The process of making a copy of DNA is called _________________________.
• DNA ____________________________________________________ of the cell cycle,
before a cell divides.
• DNA replication occurs in three steps:
o Step 1 _____________________________________________________________
that link the complementary nitrogen bases between the two strands. The ________
where the double helix separates are called _______________________________.
o Step 2 At the replication fork, ___________________________________________
_______________________. __________________________________________
to the exposed nitrogen bases, __________________________________________.
o Step 3 ________________________ that are __________________________ DNA
molecule.
(Video clip) DNA Replication What does the enzyme helicase do to DNA? ________________
_____________________________________________________________________________
What does the enzyme DNA polymerase do? _________________________________________
_____________________________________________________________________________
What is the end result of DNA replication? ___________________________________________
______________________________________________________________________________
Checking for Errors
• In the course of DNA replication, ____________________________________________
______________________________________________________________________.
• An important feature of DNA replication is that _________________________________
______________________________________________________________________
• This proofreading ____________________ in DNA replication to about _____________
______________________________________________________________________
The Rate of Replication
• Replication does not _________________ of the DNA molecule and _______________
• The _____________________ molecules found in __________________ usually have
______________________________________________________________________.
• The __________________________________________________________________
_______________________of the DNA circle.
• In ______________ cells, each chromosome contains __________________________.
• Each human chromosome is ______________________________________________
_____________________________________________________________________.
• With multiple replication forks working in concert, _______________________________
___________________________________________________.
Replication Forks Increase the Speed of Replication