Transcript Cell Cycle and Mitosis

Cell Cycle and Mitosis
Cell Cycle
• Cell Cycle = the entire
cycle of a cell from
one division to the
next
– Interphase (G1, S, G2)
= between cell
divisions
– M Phase (Mitosis and
Cytokinesis) = cell
division
Interphase
• Most of the time, a cell is in Interphase
• G1 (Gap1)
– Cell grows, copies organelles
– Protein synthesis and all normal activities of
cell (like cellular respiration) are carried out
Interphase
• S (Synthesis)
– DNA is copied
– Protein synthesis, cellular respiration occur
– Cell continues to grow, copy organelles
• G2 (Gap2)
– Cell growth continues
– Protein synthesis and cellular respiration occur
M Phase
• Mitosis = division of the nucleus
• Cytokinesis = division of the rest of
cytoplasm and its contents
• Results in 2 identical daughter cells
Duplicating Chromosomes
• Before cell division can
occur, all of the DNA must
be copied in S phase
• After duplication, you
have 2 sister chromatids
per chromosome
Sister Chromatids
• Sister Chromatids Chromosome BEFORE duplication
= identical copies
of a chromosome Chromosome
AFTER
• Centromere =
duplication
where sister
chromatids are
attached to one Chromosome
after mitosis
another
Question…
• Why do chromosomes duplicate?
– To have a copy of DNA for each new daughter
cell
Haploid vs. Diploid
• Diploid (2n)
– 2 copies of each chromosome
– All somatic cells are diploid (non-gametes)
• Haploid (n)
– 1 copy of each chromosome
– Sperm and egg are haploid
Mitosis vs. Meiosis
• Mitosis
– Results in 2 identical
diploid daughter
cells from the
original diploid cell
• Meiosis
– Results in 4
nonidentical haploid
cells from one
original diploid cell
Phases of Mitosis
•
•
•
•
•
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
“Pay Me AnyTime”
Phases of Mitosis
• Prophase (P)
– Chromosomes begin to
condense into
chromatids
– Mitotic spindle forming
• Prometaphase
– Chromosomes
condensed & attached
to spindle fibers,
nuclear envelope in
fragments
Phases of Mitosis
• Metaphase (M)
– Chromosomes line up
in the middle of the cell
• Anaphase (A)
– The spindle fibers pull
the sister chromatids
apart
• Telophase (T)
– Nuclear Envelope
reforms
Overview: Phases of Mitosis
Cytokinesis
• Cytokinesis differs
between Animal and Plant
Cleavage
cells
Furrow
• Animal Cells – forms a
cleavage furrow
– Cells narrow and pinch off
from each other
• Plant Cells- forms a cell
plate
Cell Plate
Binary Fission
• Bacteria don’t go through
mitosis
• Why not?
– No nucleus, just free floating
DNA
• Steps of Binary Fission
– Cell grows in size
– Copy DNA
– Split cell into 2 new cells
Cancer
• Cancer is uncontrolled cell growth
• Usually, the cell cycle is controlled by a
variety of checkpoints and molecules
• Cancer cells do not respond to these
checkpoints  keep on dividing
• Cancer cells no longer perform their normal
functions, steal nutrients from other cells,
crowd out other cells.