Cell Growth and Division Notes
Limits to cell growth
1. The larger a cell becomes, the more demands on its DNA
2. Trouble moving enough nutrients and wastes across the cell membrane
3. Organization
Before we talk division
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Genes located in DNA within ___The nucleus___of eukaryotic cell
DNA strand wraps around proteins to form thin threads called
_____Chromatin________
When cell gets ready to divide, DNA duplicates, then condenses into
____Chromosomes__
Humans have ___46__ chromosomes in every cell
During ___S-Phase__of the cell cycle, all 46 are copied (making an identical
copy of the original DNA)
 NOW when the cell splits in half, each new cell
has
__________________________________________________________________________________
Anatomy of a Chromosome
After Synthesis (S) phase,
each chromosome
consists of two identical
_______Sister___ __Chromatids_______
– Chromatids attached at
the _Centromere______________.
Cell Division
When a cell divides the _____# of chromosomes _____stays the same.
Common locations for cell division in a mature adult human
1. Intestinal Lining-every 24 hours
2. Skin
3. Sperm Cells
4. Blood cells/bone marrow
5. Liver cells/sometimes
Cells that stay in G0 (non-dividing) once mature
1. Muscle Cells
2. Cardiac Cells
3. Kidney
4. Nerve Cells
The Cell Cycle
G1 (gap 1 phase)
Makes sure the DNA to be replicated is healthy and the cell is a good
size
S (Synthesis Phase)
DNA is supplicated
G2 (Gap 2 Phase)
Makes sure that the DNA that was replicated is healthy and the rest of
the cells ready for division
M (M phase)
Makes sure that the chromosomes are properly attached to the spindle
Fibers.
Checkpoints and Apoptosis
As the cell goes through Cell cycle there are __
Checkpoints_______________________________.
These are to make sure that the division results in a ________________________ cell.
G1 Checkpoint: See above
G2 Checkpoint: See above
M checkpoint: See above
What happens if a cell is stopped at a checkpoint?
1. Repair the damage
2. Self-destruct (Apoptosis)
____Proteins______ regulate these processes and determine which way the cell will
go.
MITOSIS--- Nuclear division
Interphase --- NOT A PART OF MITOSIS this is really:
1. Gap 1-cell grows, doubles organelles
2. Synthesis
3. Gap 2-cell grows
The Steps of Mitosis (PMAT)
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
1. Prophase – “Pasta”
 Chromatin fibers ____condense________
 __Nuclear Membrane__ membrane breaks down
 Spindle of microtubules forms from centrioles
 [__Animals Only_______________________ only]
 Spindle fibers attach to chromatids on
____centromere____________________________
2. Metaphase- “middle”
 Chromosomes ________line up_______________ in the middle
 Spindle fibers attach _____centrioles________ to centromeres
 Every __Sister Chromatid________________ has fiber attached to it
3. Anaphase: “____Away__Phase________________”, form “A’s”
 ____Spindle Fibers__ contract
 Pull sister chromatids ___apart_____________________
 The ____chromosomes___continue to move until they are in
______two___________groups
 Each side has own copy of DNA
4. Telophase- “end phase”
 __Nuclear _membranes reform at each pole
 Chromosomes ____unwind______________________
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Spindle ______disappears___________________
Cytokinesis
 ________NOT __a phase of Mitosis
 During cytokinesis, the cytoplasm __cuts in
half________________________________________.
 Each daughter cell has an ____identical_____ set of duplicate chromosomes
Cytokinesis in Plants
In plants, a structure known as the ____Cell Plate____ forms midway between the
divided nuclei.
Cytokinesis in Animals
Animal cells contract an _actin_fiber across middle of cell and “pinch” into
_______2______new cells (daughter cells).
Terms:
A. Spindle: network of microtubules that move chromosomes during
mitosis and meiosis
B. Equator: center line of cell where chromosomes line up during
metaphase
C. Poles: the opposite ends of the polls
D. Centrioles: Animal cells ONLY, organelle that helps with cell division
E. Cleavage Furrow: The pinching in of an animal cell during cytokinesis
F. Cell plate:
disk in plant cells that divide the cell into two daughter cells during
cytokinesis
G. Centromere:
Region where two sister chromatids are joined tightly together
Results of Mitosis
A. Production of 2 new ____daughter_________________ cells
B. Daughter cells are ___exactly______the same as original
_____parent____________ cell
C. Cell --> Tissue --> Organ --> Organ System --> Organism
Proteins that control Cell Cycle and growth
 Cell cycle regulated proteins called
__cyclins___________________________________
The amount and type rises and falls in time w/ the cell cycle
 Cyclin: because it regulates cell __cycle____________________
Regulate the timing of cell cycle in eukaryotic cells
Cancer is:
Cancer is a disorder in which some of the body’s own cells lose the
ability to control growth
Cancer cells do not respond to the signals that regulate the growth of most
cells.
 Divide uncontrollably
 Don’t stop at _____Checkpoints____ and do not do
__Apoptosis____________________________
 Form masses of cells called ____Tumors_________________________
 _____Metastasis____: tumor cells break loose and spread in body
Causes of Cancer: Carcinogens
 Genetics
 Chemicals- asbestos, cigarettes,
formaldehyde, dioxins, chlorine, pesticides
 Radiation
 Certain viruses (HPV)
 Poor Diet/ Obesity
Prevention of Cancer
 Genetic screening BRCA 1 and BRCA 2
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Do not smoke, drink too much, proper
diet, exercise, prevent sunburns, proper
health screenings