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Notes: DNA Structure and Replication (Ch. 12-1, 12-2)
DNA is one of the 4 types of macromolecules known as a _______________. DNA stands for
_________________________________.
Components and Structure of DNA
DNA must be able to:
1.
carry genetic information from ________________ to the ______ (genes are made of DNA)
2.
be easily and _____________ copied before ________________________.
The ___________ (repeating subunits) that make up nucleic acids like DNA are called
_____________________________.
Each nucleotide contains 3 parts:
1.
Nucleotide
structure
2.
3.
a. purines (________ rings)
i.
ii.
b. pyrimidines (____ ring)
i.
ii.
When nucleotides bind together, they form a chain, which is the
______________ DNA.
1. the sugar and phosphate groups form the _____________
of the chain (sides of a ladder)
2. the nitrogenous bases stick out sideways from the chain (rungs of the ladder)
The chain has a direction determined by whether the sugar is right side up, or upside down. The
“top” of the molecule will have a ______________________________, and the sugar will be
___________. It is known as the _________ (pronounced 5 prime). If the sugar is pointing down
and there is no phosphate sticking out, it is the __________ (pronounced 3 prime). It looks like a
twisted ladder. The strands run in opposite directions; this is called _________________ (like
opposite flows of traffic).
Chapter 12: DNA and RNA
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Discovery of the Structure of DNA
1. Chargaff’s Rules:
Erwin Chargaff (1905-2002) discovered that in any
DNA sample, the amount of guanine in a DNA sample
is always equal to the amount of _____________,
and that the amount of adenine was always equal to
the amount of
___________. This eventually led to our _____
__________________. Adenine from one strand and thymine from the other always pair together
with _____________________, and guanine on one strand and cytosine on the other strand always
bond together with ________________________________.
If there was a DNA strand with the following bases, what would the opposite, or complementary,
strand have?
ATTAGCAGGAATACG
__________________________
2. X-ray evidence (1952):
Rosalind _________ studied the DNA molecule using _______________________ (bending of
waves around an edge or barrier) to see the structure of DNA. She aimed a powerful x-ray beam at
DNA samples and recorded the scattering pattern of the x-rays on film. From her work she was able
to see that the DNA strands were ______________________________ forming a ____________.
3. The Double Helix Model (1953):
Francis _____ and James __________ were trying to figure
out the structure of DNA by building models with cardboard
and wire. When they saw Franklin’s pictures they soon were
able piece all the information together to come up with the 3dimensional structure of DNA: a ______________ with two strands winding around each other.
DNA and chromosomes
DNA molecules are extremely long. In order to fit into cells, they must _______ as much as possible.
In humans, the amount of DNA in the nucleus is more than ________________________.
Remember, in eukaryotic cells the DNA is bound to _____________ forming __________________.
To fit the DNA into the nucleus, the DNA and associated proteins are packed tightly a process called
____________.
Chapter 12: DNA and RNA
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Chromosomes
DNA double helix
______
_______
DNA Replication: How is DNA copied?
The process of copying DNA is called ____________________. Because DNA is double stranded,
each strand can be used as a ___________. to make the other strand through the process of _____
__________. Because of this, the two strands are called _________________ (think about angles in
Geometry).
During DNA replication (basic):
1.
the DNA is unwound and _________ by the
Original
DNA
enzyme _______________________.
2.
The strands are held apart by ______________
_______________ aka__________
3.
each original DNA strand is used as a
__________ (or model) to make a new DNA
New DNA
(one old
Several enzymes are involved in DNA replication
strand,
a. The enzyme Primase ______________
one new
_______________________________________________________________
strand)
strand with complementary base pairing
4.
b. Another enzyme, called ___________________________, adds new bases to the new
RNA primer. It always reads the strand from _______ to _____ and lays down the new
strand from _____ to _______. This occurs continuously in the direction following
Helicase opening up the replication fork. For this reason, this strand is known as the
________________________________.
c. Another ________________________ also “_______________” the new DNA to check
for errors.
d. Meanwhile, on the other strand, known as the ___________________________,
Primase and DNA Polymerase synthesize DNA from ____ to _____ away from the
Chapter 12: DNA and RNA
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replication fork. These small spurts of replication form what are known as
_________________ ___________________.
e. The _________________ ____________________ are joined together by the enzyme
______________.
f. On both strands, the RNA Primer is replaced with DNA nucleotides by the enzyme
__________________________.
g. When replication is complete, each DNA molecule is made of one __________ and one
______________. This is described as _______________________. The new DNA
molecules are rewound by the enzyme _________________.
Chromosome Arrangement
Prokarytoic cells (__________)
1. Prokaryotic cells have one circular chromosome that is _______________ in the cytoplasm.
Remember, prokaryotic cells do not have a __________________.
2. When prokaryotic cells copy their DNA, the process begins at __________________ in the
chromosome and moves around the circle in ________________________ until complete.
Eukaryotic cells
1.
Eukaryotic cells have more chromosomes than prokaryotic cells, and DNA replication
begins at ____________________________ and continues in both directions until each
chromosome is completely copied.
2.
DNA Polymerase only works in _______________. One strand is read and synthesized
_______________ while the other is synthesized __________________________.
Chapter 12: DNA and RNA
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