Name __________________________________________________________________
Test Date _____________________
UNIT 6 - DNA & THE CELL CYCLE
The third statement of the Cell Theory states that all cells come from ____________________________________. The continuity of life is
based on the reproduction of cells or ____________________________. In most organisms, cells increase to a certain size and then
divide into two cells. This cycle of growth and cell division is known as the _________________________. The cell cycle is defined as
the period of time from the beginning of one _______________________________ to the ______________________________________.
This type of cell division is _________________ reproduction. In asexual reproduction, the genome or ________________ of the cell is
exactly replicated resulting in ________ ___________________ cells.
I. IMPORTANCE OF ASEXUAL REPRODUCTION (p. 241-243)
A. Single-celled Organisms
Single-celled organisms belonging to kingdoms ___________________, ______________________, _______________, and
____________, use asexual reproduction to ___________________________________________.
B. Multicellular Organisms
1. Growth & Development – Organisms grow through ___________________________, rather than unlimited growth of a cell.
 Surface Area to Volume Ratio – As the size of an object increases, the __________________ increases at a much
faster rate than the _____________________; therefore, the surface area to volume ratio becomes a ______________
number.
 In a cell, the ________________________ represents the surface area and the ________________________
represents the volume. At a certain point, a cell can no longer meets its needs and maintain _____________________;
therefore, cells only grow to a certain size.
2. Renewal & Repair – Cell division is used to replace cells that die from normal wear & tear; for example, ________________
and __________________. Other types of cells maintain the ability to divide, but keep it in reserve unless severely damaged;
for example, _____________________________. Other cells do not appear to divide at all in a mature human; for example,
____________________ and __________________________.
II. CELL CYCLE IN PROKARYOTES (p. 475)
All __________________________ undergo a type of cell division known as _______________________. Binary fission is a less
complex, faster process than eukaryotic cell division because bacteria lack a _____________________, ______________________
___________ and have only _____________ chromosome.
III. CELL CYCLE IN EUKARYOTES - AN OVERVIEW (p. 245)
There are two main parts to the eukaryotic cell cycle:
A. Interphase - Accounts for about ________ of cell cycle. This is the period of time in which a cell is carrying out _______________
________________________. __________________ synthesis is occurring at a high rate. The cell’s DNA is in the form of
_______________, long, fine strands of DNA wrapped in ___________________________.
B. M-Phase – Period of time in which cell division occurs. Consists of two main events:
 Mitosis – Division of the ____________________________
 Cytokinesis – Division of the _________________________
IV. A CLOSER LOOK AT INTERPHASE
There are three stages to interphase:
 G1 - Cell ______________, carries out normal cell activities such as _________________________________________.
Period in which ________________ production is highest
 S - _______________________. Replication of ___________; known as the “________________________________”.
Replication takes place in the _____________________ of the cell.
 G2 - Preparation for _____________________. ______________________ are replicated in ____________________ cells.
At the end of interphase . . .
________________
replicated
________________
_____
Protein microtubules that
will form spindle fibers

_________ has been replicated – still in
_______________________ form.
_______________________ have been replicated in
__________________ cells only. Results in 2 pairs of
centrioles, composed of _____________________.
The ___________________ and ________________
are still present.


_____________
_________
_
____________________
V. A CLOSER LOOK AT MITOSIS (pp. 246-248)
Mitosis, also known as the _M - Phase_, is described in four stages, but it is a continuous process.
A. PROPHASE – In prophase, the nucleus is preparing to divide. This includes . . .
_________________________

____________________
____________________



______________________
________________________
______________________ and ___________
_______________________ disassemble.
Replicated ___________ thickens & condenses
 results in ______________ made up of 2
________________ _____________________
held together at the _____________________
_________________________ begin moving
to opposite poles of the cell.
________________________ form
_________________________________.
Specific spindle fibers attach to the sister
chromatids at the ______________________.
centromere). Other fibers, known as non-kinetochore
B. METAPHASE – In metaphase, the sister chromatids are organized in the microtubules
___________________
cell.
span the cellofto the
aid in
support and
structure.

_____________________

______________________
________________
__

______________________
_____________________ network is fully formed
with ________________ at opposite ends.
Each ______________________________ is
attached to a spindle fiber at the _______________
located at the ______________________________
Sister chromatids align at the _______________ of
the cell.
C. ANAPHASE – In anaphase, the sister chromatids are pulled ________________________.
______________________
______________________
______________________




_________________
________________________
________________________
D. TELOPHASE – By the end of telophase . . .

____________




______________
_________________________ split.
Sister _____________________ are pulled
apart by ___________________________;
move to opposite ends of the cell.
Genetic material is now known as daughter
_______________________.
Cell elongates; prepares for two new nuclei.
Complete and _____________________ set of
_____________ at each pole of the cell.
___________________________ disassemble.
New ____________________________ forms around each
group of chromosomes.
DNA uncoils  _____________________
____________________ reforms 
___________________ are produced _______________
resumes  cell ________________________ resumes
__________________
E. CYTOKINESIS – This refers to the actual division of the _______________________. Cytokinesis begins during
__________________ and differs in plant versus animal cells because plant cells have a _______________.
1. Animal Cell – In the final stages of telophase, the ______________________________ pinches in. This is referred to as a
_________________________ and is due to the action of ______________________________. This cleavage furrow
deepens until the parent cell is pinched in two, producing two separate, _______________________ daughter cells.
2. Plant Cell – There is no cleavage furrow in plant cells. Instead, during late telophase, ___________________________ from
the _______________________________________________ move to the center of the cell where ______________________
and other materials they contain come together to form a _______________________________________, which eventually
develops into a ___________________________.
_____________________________
_
_____________________

___________________ Cell
_____________
____________
_______
_______
_
______________________ Cell
_____________________
_____________________
VI. CONTROL OF THE CELL CYCLE
(pp. 250-253)
A. Timing of the Cell Cycle
The timing of the cell cycle is regulated by proteins known as ____________________ that bind with enzymes known as
________________ to form a complex called ___________________________________________ or ___________. These
______________ are responsible for monitoring checkpoints in the cell cycle.
 If the progression of the cell cycle is too slow, ____________________________________________________________
________________________________________________________________.
 If the cell cycle progresses too quickly, the result is uncontrolled cell growth or ______________________. This is
harmful for many reasons
o If a cell spends all of its time dividing, _______________________________________________________
o The rapidly- dividing, nonfunctional cells steal ___________________ from healthy, functioning cells causing
____________________.
o The rapid replication of _____________ results in a greater risk of _____________________.
B. Stem Cells
Stem cells are _________________________ cells that have the ability to _________________________________. Stem cells
that can give rise to many types of cells are said to be ___________________________. Although stem cells are found in certain
locations in adults, most research involves the use of ______________________ stem cells, due to the fact they are
considered to be “________________________” and capable of unlimited specialization. Scientists hope that stem cells may be
used as implants to replace ____________________________________, but there are many _____________________ and
__________________ concerns.
C. Number of Cell Divisions per Cell
Each cell is programmed to divide a certain number of times, and then it will not divide again. This is monitored by
_______________________, a series of DNA ________________________ found at the tips of each ____________________.
As DNA is _____________________ in ___________ of the cell cycle, the telomeres shorten. Once they reach a critical length,
the DNA does not replicate again, and the cell does not ______________________. _________________________________
and _____________________________ produce an enzyme known as _______________________________, which restores the
chromosomes back to their original length, thereby theoretically making the cell capable of ______________________ cell
division.
A CLOSER LOOK AT DNA & REPLICATION
I. DNA – THE DISCOVERY OF THE MOLECULE OF INHERITANCE (pp. 287-294)
DNA contains the _________________________ and the _______________________________ for a cell. Scientists in the early
1900s realized that inheritance was dependent on __________ found on ____________________ and that chromosomes were
composed of ___________ and ____________________. It wasn’t until the 1940s that scientists established _______ as the
molecule of inheritance, and still another 15 years passed before the structure of DNA was discovered.
A. Griffith (1928)
 Discovered that bacteria can take up genetic material from environment in a process known as _____________________.
 Performed experiments with _____________ and bacteria known as _____________________.
o Mixed harmless living bacteria with dead ______________________ bacteria and injected them into mice.
o Mice died.
B. Avery, et.al. (1944)
 Set up experiments to identify “transforming substance” discovered by Griffith
 Used enzymes that destroyed carbohydrates, lipids, proteins, and RNA . . . transformation still occurred. Used an enzyme
that destroyed DNA, ___________________________________________________________________________.
 Concluded that _________________ stores and transmits the genetic information from one generation of an organism to
the next.
 Scientific community did not completely accept their conclusion
C. Hershey & Chase (1952)
 Used a virus known as a ________________________________ which infects __________________.
 Viruses are composed of ______________and ______________; require a _________ cell in order to replicate.
 Hershey & Chase recognized that virus must inject its genetic material into the bacterial cell for replication to take place.
 Used labeled ______________________ to determine whether DNA or protein was injected into bacterium.
 Hershey & Chase concluded that the genetic material of the bacteriophage was ________________.
D. Watson & Crick (1953)
 Used molecular models to solve the 3-dimensional structure of DNA
 “Borrowed” an x-ray of DNA taken by ________________________________________ to solve the puzzle
 Proposed a ___________________________ structure with a backbone of alternating __________________ and
_________________________ with ________________________________ paired in the middle
II. STRUCTURE OF DNA
 ___________________________________ is a ___________________________ made up of ____________________
monomers. Each DNA _____________________ is composed of :
o _________________________
o _________________________
o _________________________
 Strong, stable ________________ bonds hold the components of each nucleotide together.
 In addition, nucleotides form strong ________________ bonds with other nucleotides, resulting in a long strand of
nucleotides.
 Double helix created by ______________________ bonding between ________________________
 The diameter of DNA is uniform due to specific pairing of nitrogen bases
o Purines – double-ringed nitrogen bases
 _______________________
 _______________________
o Pyrimidines - single-ringed nitrogen bases
 _______________________
 _______________________
o ______________________ always base pairs with a ______________________, specifically …
 _____________________ base pairs with _____________________
 _____________________ base pairs with _____________________
o _______________ and ____________________ determined this structurally because the _______________ of
DNA is uniform.
o ___________________ determined this chemically. His chemical analysis of DNA from many different organisms
always showed that the % of adenine = % _______________ and the % of guanine = the % _______________.
These findings are known as ______________________________________________.
 The two strands of nucleotides are ________________________________; that is, they run opposite to each other.
 It is the _________________________ and _________________ of nucleotides that makes each gene unique.
DEOXYRIBONUCLEIC ACID
adenine
covalent bond
cytosine
deoxyribose
guanine
hydrogen bond
nitrogen bases
nucleotide
phosphate group
purines
pyrimidines
thymine
5’ end
3’ end
III. DNA REPLICATION (pp. 295-299)
Prior to _______________________, the DNA must __________________. This occurs in _____ of _____________________.
During this part of the cell cycle, DNA is in the form of _____________________. DNA can replicate itself exactly due to
________________________________. Replication occurs in the _________________ of the cell and requires the participation of
several _____________________.
Replication may be summarized in the following steps:
 DNA is “unzipped” by the enzyme, ________________. Helicase breaks the ______________________ bonds between
the _____________________. The point where the unzipping begins is known as the ____________________________.
The continuation of the unzipping is called the _________________________________. This occurs in several places in
each __________________, much like a __________________________________.
 ___________________________________________ hold the separated DNA strands apart.
 Another enzyme, ____________________________ moves ahead of the _________________ to relieve tension in the
double helix as it is being unzipped.
 The enzyme, ____________________________ adds nucleotides to both sides of the DNA molecule according to
_________________________ rules; however, DNA polymerase has two restrictions:
1) It can only add nucleotides in a ________________________ direction.
2) It can only add nucleotides to an existing strand.
 Before DNA polymerase begins moving in nucleotides, an __________ _______________________ must be put in place.
Eventually this primer is removed and replaced with DNA nucleotides.
 The two sides of the DNA molecule are replicated differently because nucleotides can only be added in a
_______________ direction:
o One side of the DNA molecule is being replicated in the same direction as the __________________________.
This is known as the _______________________ strand. Nucleotides are moved in by _____________________
in a _______________ direction as the DNA is unzipped.
o On the other side of the DNA molecule, nucleotides are added ________________ from the replication fork. This
is known as the _____________________ strand. Short segments of nucleotides are synthesized, each with a
new _____________________, as the DNA is unzipped. These short segments are known as
________________ _____________________. Eventually, another enzyme known as __________________
“glues” together the ________________________ fragments to create a continuous strand of nucleotides.
 Another type of _____________________________________ proofreads the replicated DNA to minimize the chance of
________________________.



The result is two _____________________ DNA molecules, each new DNA consists of one _________________ strand
and one ________ strand. This is known as the _________________________________ model of replication.
These two identical DNA molecules are the _________________________________________ that proceed through
______________________.
Once replication has been completed, the cell moves into ________ and then, ________________ of ________________.
IV. A DETAILED VIEW OF DNA REPLICATION
…………………………………………………………………………………………………………………………………….
THE EUKARYOTIC CELL CYCLE
DNA
…………………………………………………………………………………………………………………………….
DNA REPLICATION