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9.1 Overview of
Cell Division Mechanisms
 Individual cells or organisms produce offspring by the process of
_______________

When a cell reproduces, each descendent receives information coded in _______,
and enough _______________ to begin operating
Mitosis, Meiosis, and the Prokaryotes
 Eukaryotic cells
• ___________________ copies DNA and divides a nucleus, producing two
____________________ nuclei
• ____________________ is a nuclear division that produces
_______________gametes for sexual reproduction
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____________________ cells reproduce asexually by ________________ fission
Each species has a characteristic number of ________________ that differ in
length and shape
 Each consists of one double strand of __________
 After duplication, each consists of _________double strands (sister
_______________) that remain attached to each other at a
________________until late in nuclear division
A chromosome consists of DNA that is wrapped around proteins
(_____________) and _________________
Each histone and the DNA wrapped around it make up a ________________, the
smallest unit of structural organization in chromosomes
Individuals have a characteristic _______________ of chromosomes in each of
their cells
The chromosomes differ in ______________ and _______________, and they
carry different portions of the cell’s hereditary information
 Division mechanisms parcel out the information into descendent cells
9.2 Introducing the Cell Cycle
 Cell cycle
• A sequence of three stages
(________________,_________________,_________________ division)
through which a cell passes between one cell division and the next
 ___________________ consists of three stages, during which a cell increases in
size, doubles the number of cytoplasmic components, and duplicates its DNA
• ______: Interval of cell growth and activity
• ________: Interval of DNA replication (synthesis)
• ________: Interval when the cell prepares for division
 Most cell activities take place during ________

Control mechanisms work at certain points in the cell cycle; some can keep cells
in _______

Loss of control may cause cell death or _______________
Mitosis and the Chromosome Number
 Mitosis produces two _____________ nuclei with the same number and kind of
chromosomes as the parent
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Chromosome number
• The sum of all chromosomes in a type of cell
• Human cells have _____ chromosomes paired in ______ sets (diploid
number)
• Pairs have the same shape and information about the same traits (except
_________________________)
Bipolar spindle
• A dynamic network of _______________ that forms during nuclear
division
• Grows into the cytoplasm from opposite poles of the cell and attaches to
duplicated chromosomes
• Microtubules from opposite poles attach to different
_________________________ and separate them

A cell cycle starts when a new cell forms by division of a parent cell, and ends
when the cell completes its own division

A typical cell proceeds through intervals of
________________,______________,___________________ division
9.3 A Closer Look at Mitosis
 When a nucleus divides by mitosis, each new nucleus has the same
_____________________________ as the parent cell
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There are four main stages of mitosis: prophase, metaphase, anaphase, and
telophase
Prophase
 _________________
• Chromosomes _________________
• ___________________ form a bipolar spindle
• Nuclear envelope __________________
• __________________ attach to the chromosomes

_______________________
• A region near the nucleus that organizes spindle microtubules; usually
includes two ___________________
Metaphase and Anaphase
 ___________________
• All duplicated chromosomes line up _____________ between the spindle
poles

___________________
• Microtubules separate the ________________________ of each
chromosome and pull them to _________________ spindle poles
Telophase
 ______________________
• Two clusters of chromosomes reach the spindle _______________
• A new nuclear envelope _____________ around each cluster
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Two new nuclei are formed, each with the same chromosome number as the
parent cell
Mitosis divides the __________, not the _______________
Mitosis has four sequential stages: prophase, metaphase, anaphase, and
telophase
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A bipolar spindle forms; it moves the cell’s duplicated chromosomes into two
parcels, which end up in two genetically identical nuclei
9.4 Cytoplasmic Division Mechanisms
 In most kinds of eukaryotes, the cell cytoplasm divides between late
________________ and the end of _____________________, but the mechanism
of division differs

_____________________
• The process of ______________________ division
Cytoplasmic Division
in Animal and Plant Cells
 Animal cells
• A ____________________________ partitions the cytoplasm
• A band of actin filaments rings the cell midsection, contracts, and pinches
the cytoplasm in two
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Plant cells
• A _______________________ forms midway between the spindle poles;
it partitions the cytoplasm when it reaches and connects to the parent cell
wall
After nuclear division, the _________________ divides

One nucleus ends up in each of two new cells
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In animal cells, the cytoplasm pinches in two
 In plant cells, a cross-wall forms in the cytoplasm and divides it
Cell Cycle Controls
 Checkpoints in the cell cycle allow problems to be corrected before the cycle
advances

___________________ produced by ______________________________
interact to advance, delay, or stop the cell cycle
• _________________ can activate other molecules to stop the cell cycle or
cause cells to die
• __________________________ can activate kinases to start mitosis
Checkpoint Failure and Tumors
 When all checkpoint mechanisms fail, a cell loses control over its cell cycle and
may form a _______________ (abnormal mass) in surrounding tissue

Usually one or more _______________________ products are missing in tumor
cells
• Tumor suppressor gene products _______________ mitosis
• __________________________ products stimulate mitosis
Neoplasms
 Neoplasms
• ________________________of cells that lack control over how they
______________ and _________________
• Benign _________________ (such as ordinary skin moles) stay in one
place and are not cancerous
• ___________________ neoplasms are cancerous
Characteristics of Cancer Cells
 __________________ (malignant neoplasms)
• Cells grow and divide ___________________; capillary blood supply to
the cells may increase abnormally
• Cells may have altered plasma membrane and cytoplasm; metabolism may
shift toward fermentation
• Cells have altered __________________________ and weakened
adhesion; may break away and invade distant tissues
(____________________)
 Built-in mechanisms monitor and control the timing and rate of cell division

On rare occasions, the surveillance mechanisms fail, and cell division become
uncontrollable
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Tumor formation and cancer are the outcome