cell cycle Flashcards
new cells are clones…
same DNA of original cells (except reproductive cells)
cell cycle phases
Cell division
Cells performing normal functions
chromosomes
pieces of DNA
somatic cells
everything that is not a reproductive cell
somatic cells contain…
46 chromosomes, 23 pairs
where do cells spend most time?
interphase; performing normal functions
interphase: cells begin preparations for
division
interphase subphrases:
G1, S, G2
G1:
first gap phase: growth and organelles copied
S:
synthesis phase: DNA is copied
G2:
second gap phase: proteins made that assist division
mitosis produces..
exact copies of parent cell nucleus (in somatic cells)
big pic of mitosis:
reorganization of chromosomes into new cells
stages of mitosis:
- Prophase
- Metaphase
- Anaphase
- Telophase
mitotic spindle function
arranges chromosome during division
mitotic spindle: centrosome
o In animal cells
o Microtubules grow outward
o Support cell shape and assists with cell division
mitotic spindle: kinetochore
o Center of chromosomes
o Connects identical sister chromatids
o Attachment site for microtubules
what occurs during prophase?
*Chromosomes condense
*Mitotic spindle forms
-Centrosomes move apart
what happens between prophase and metaphase (pro-metaphase)?
*Nuclear envelope breaks down
*Chromosomes become completely condensed
*Microtubules attach to kinetochores/lengthen cell
where are centrosomes during metaphase
at opposite sides of cells
what do chromosomes do during metaphase
each chromosome attached to both centrosomes
metaphase plate
region where chromosomes are lined up by microtubules (center of cell)
anaphase: chromosome copies…
separate
telophase and cytokinesis
- Nucleus forms at each end
- Chromosomes become less condensed
- Cytoplasm divides
cytokinesis:
physically separating original cell into 2 daughter cells
*Microtubules are removed
how to prokaryotes undergo “cell division”
binary fission:
*Form of asexual reproduction
*Cells elongates, duplicates chromosome (sometime just 1) and splits in half forming 2 new individuals
cell cycle control system:
coordinates key events in cell cycle
cell cycle stops at…
specific checkpoints: G1, G2, metaphase
cell cycle progression is managed by
cyclic proteins
G1 checkpoint:
determines if cell will continue dividing
-ensure cell has proper nutrients
-check if more cells are needed (presence of growth factor?)
g1 checkpoint: if growth factors are NOT around and division should not occur…
they go into G0 phase ( can go back to G1 if growth factors are present again)
G2 checkpoint:
ensures DNA has copied properly (2 complete copies of DNA)
M checkpoint:
ensures all chromosome kinetochores are connected to microtubules
density dependent inhibition
if closely packed, they will not keep dividing
anchorage dependence
cells only divide if they are attached to something
Cycle checkpoints are regulated by proteins, but
mutations may make a protein that does not work right
Mutations in cell cycle regulating proteins may lead to
unregulated cell cycle, which can lead to tumors or cancer
cancer cells lose…
density dependent inhibition: continue to divide even when closely packed with other cells
(tumors form very dense tissue)
tumor:
uncontrolled cell growth formed by one abnormal cell that evaded immune system
benign tumor
cannot leave original location
malignant tumor/cancer
can lose cells that spread to new locations (metastasis)
o Chemotherapy interferes with
cell cycle: blocks cell division to let immune system get ahead of cancer cells
-Hurts cancer cells most since they are dividing fastest
