This site is 100% ad supported. Please add an exception to adblock for this site.

Biology Chapter 12 2


undefined, object
copy deck
What are the key roles of cell division?
The continuity of life based upon the reproduction of cells or cell division

the creation of duplicate offspring that provides for growth, development and repair
Unicellular Organisms
1 mother cell divides and ends up with 2 identical daughter cells
Multicellular Organisms
development from a fertilized cell


A cell's complete complement of DNA/genetic information and are packaged into chromosomes
Eukaryotic Chromosomes
Consist of chromatin, a complex of DNA and protein that condenses during cell division.
Gemete Cells
one set of chromosomes
Somatic Cells
2 sets of chromosomes
Cell cycle phase
G1 phase - growth (protein synthesis)

S phase - DNA Synthesis - each chromosome duplicates into 2 sister chromatids, connected at the centromere

G2 phase - growth (protein synthesis)

M phase - mitosis or meiosis - division of nucleus, Cytokenesis - division of cytoplasm and other organelles the cell physcially divides

If cell stops dividing and leaves cell cycle, the cell enters G0 phase and is not duplicatiing
Divides nucleus into identical copies

Consists of 5 distinct phases PPMAT

Prophase - chromosomes condense

Prometaphase - mitotic spindle attaches

Metaphase: chromosomes line up in the center mitotic spindle pulls apart the chromosomes to create daugher chromosomes

Anaphase - sister chromatids separate and move to different poles

Telophase - nuclear envelopes form
(animals) The physical division of cells producing 2 separate, genetically equivalent daughters

Forms cleavage furrow involving the cytoskeleton

(plants) the cell wall builds cell plates to separate the sisters
produce microtubles and mitotic spindle

Acts as the poles of the spindle
Organelle made out of microtubles found in animal not plant cells.

At the poles of the cells pulling the sisters apart
Central point that connect the sister chromosomes
motor proteins at centromeres that moves chromosomes - like a winch in a car
How do prokaryotes reproduce?
by a process known as binary fission
the process that separates the two daughter cells in animals.
Cleavage furrow
forms on the cell surface as a ring of actin microfilaments interacting with myosin proteins begins to contract on the cytoplasmic side of the membrane.

Cleavage furrows deepen wuntil the divising cell is pinched in two.
Cell Plate
forms from the fusion of membrane vesicles derived from the Golgi apparatus. The membrane of the enlarging cell plate joins with the plasma membrane, separating the two daughter cells. A new cell wall developes between the cells from the contents of the cell plate.
Cell cycle is regulated
the frequency of cell division varies with the type of cell

These cell cycle differences result from regulation at the molecular level
Cell Cycle Control System
consists of a set of molecules that function cyclically, coordinating the events of the cell cycle

Important internal and external signals monitor to determine whether the cell cycle should proceed past the 3 main chckpoints in g1, g2 and M phases

If no proceedure takes place the cell goes to G0 phase.
Protein Kinases
enzymes that activate or inactivate other proteins by phophrylating them.
Stop and Go checkpoint signals
both internal and external signals

MPF (maturation or (M phase) - promoting factor) activates a protein breakdown process that destroys its cyclin and MPF activity during anaphase

(stop signal) Density-dependent inhibition - crowded cells stop dividing

(go signal)
anchorge dependence - cells must be attached to a surface to divide.
Cancer Cells
exhibit neither density-dependent inhibition or anchorage dependence

do not respond normally to the body's control mechanisms

Form tumors

Benign tumor remains at site of orgin

malignant tumors invade surrounding tissues and can metastasize exporting cancer cells to other parts of the body where they may form secondary tumors

Deck Info