Cell Cycle
 Asexual Reproduction
ALL substances must pass through a cell
membrane to enter and exit a cell
 smaller cells  higher surface-area-tovolume ratio  can exchange materials
faster
 cell division occurs when a cell reaches a
certain size

Asexual Reproduction
 purpose:
 in simpler organisms: reproduction
of offspring
 in complex organisms: increase
number and size of cells; repair
damaged cells
 only 1 parent is required
 parent DNA is passed onto offspring,
therefore, offspring are IDENTICAL to
 Types of Asexual Reproduction
Prokaryotes
(bacteria):
 binary fission:
1 bacteria cell
divides into
2 bacteria cells
of the same size

Types of Asexual Reproduction
Hydra
Eukaryotes
(protis
 budding: part of
t)
the parent organism
pinches off and
forms a new
organism.
Yeast
(fungu

Types of Asexual Reproduction
Eukaryotes
 mitosis: division of the nucleus into 2
nuclei
 chromosomes: carry the DNA
 chromosome #
varies between
species
 humans46 chromosomes
(23 pairs)
 Cell cycle: repeating sequence
of cellular growth and division
during the life of an
organism; check points trigger the
next stage of the cycle
growth,
preparation to
divide
 Loss of Control of the Cell Cycle
 if checkpoints are not working
properly, the cell cycle can cause
the cell to grow
uncontrollably
 leads
to cancer
http://outrea
ch.mcb.harv
ard.edu/anim
ations_S03.ht
m
Cell Cycle
http://www.cellsalive.com/cell_cycle_js.htm
1. Interphase (G1, S, G2) – cell
grows, prepares to divide and
DNA replicates
2. Mitosis: nucleus divides; each
nuclei winds up with the same #
and kind of chromosomes as the
parent
3. Cytokinesis: division of
cytoplasm
http://www.cellsalive.com/mitosis.htm
 DNA
replicates in
interphase
 nucleus
disappears

chromosome
s line up on
equator

chromosome
s separate
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
no cell wall
cell wall
Mitosis
parent
cell
46
chromosomes
92
chromosomes
46
chromoso
mes
daughter
cells
46
chromoso
mes
 Results of Mitosis
 offspring (daughter) cells are
about equal in size
 each daughter cell receives ½
the cytoplasm and organelles of
the parent cell
 each daughter receives an
IDENTICAL copy of the parent
cell’s chromosomes (DNA)