Cell Division
The Cell Cycle and Cancer
The Phases of the Cell Cycle
Cell Division / Cell Cycle
Prokaryotes
• Chromosomes are
simple, circular pieces of
DNA
Eukaryotes
• Multiple chromosomes, also
mixed with proteins and wound
tightly
– Called *Chromatin (looks like
a clump of yarn)
• Occurs rapidly
• Cells grow, replicate
DNA, then divide in two
– Called *Binary Fission
• Results in two genetically
identical cells
• # Chromosome varies in
organisms
• Cycle takes more time than
prokaryotes, and more
complex
Confusing Chromosome Vocabulary
• Chromosome –
bundles of DNA
• Chromatin – DNA
uncondensed, looks
like tangled strings
• Chromatid (sister
chromatid) –
individual strand of
condensed DNA
How many
chromosomes
are in the cell
above?
Interphase – “in between” period of growth
•
•
•
•
Majority of a cell’s life is in interphase
G1, S, G2 phases
G1 = growth of cell
S = synthesis (or replicating)
of DNA – 2x the DNA
• G2 = prepare for mitosis (make
extra organelles or structures needed for
mitosis)
Mitosis = 4 Stages = PMAT
Prophase
•
•
•
•
Longest phase of mitosis
DNA condenses (becomes visible)
Spindles are formed by centrioles
Nuclear envelope starts breaking down
Centromere – where 2
identical chromatids attach
to each other
Metaphase (PMAT)
• Shortest phase of mitosis
• Centromeres align the chromosomes
across the middle of the cell
• Spindle fibers attach to centromeres
HINT:
Metaphase = Middle
Anaphase (PMAT)
• Sister chromatids pulled apart by spindle
fibers
• Chromosomes (or chromatids) go to
opposite ends of the cell
• Separate chromosomes into two groups
HINT:
Anaphase = Away/Apart
Telophase (PMAT)
• Last phase of mitosis (PMAT)
• Chromosomes spread out into a tangle of
chromatin (stringy-looking)
• Nuclear envelope reforms around both
clusters of chromosomes
• Spindle fibers break
down
• Cell cycle is ALMOST
complete
Cytokinesis
• Cell’s cytoplasm divides to make 2 cells
• *Animal Cells: cell membrane is flexible
and pinches in 2
• *Plant Cells: cell wall is not flexible and
must create a cell plate, forming 2 plant
cells
• Now have 2 IDENTICAL
cells (same DNA - clone)