Theme 4: The Cell Cycle
11.1 Cell Division
• The process by which a single cell becomes two daughter cells
• Requirements of cell division:
◦ Two daughter cells must each receive the full complement of
gene=c material (DNA) present in the parent cell
◦ Parent cell must be large enough to divide in two and s=ll
contribute sufficient cytoplasmic components (like proteins, lipids,
etc.) to each daughter cell
• So, cellular components must be duplicated before cell
division occurs
• Prokaryo=c cells divide by binary fission
• Eukaryo=c cells first divide the nucleus during mitosis and then, divide
the cytoplasm into two daughter cells during cytokinesis
◦ Note: Adult stem cells can only replace non-reproducing
specialized cells
• Example: When skeletal muscle is damaged, quiescent (i.e.
non-dividing) satellite stem cells present in the basement
membrane of the muscle =ssue are ac=vated from their
dormant G0 phase and begin to divide to enable muscle
regenera=on
▪ Ac=va=on of satellite stem cells leads to prolifera=on,
differen=a=on and fusion of muscle precursor cells
(i.e. myoblasts) which become the muscle cells of the
myofibers
◦ Mitosis likely evolved from binary fission
11.1.1 Prokaryo7c cells reproduce by binary fission.
• Bacteria, archaeons, chloroplasts and mitochondria divide by binary
fission
• Binary Fission: A cell replicates its DNA, increase in size, and divides into
two daughter cells
, ◦ As determined by studying E. coli:
▪ Just aWer step 4, when the cell is ~2x its size and the
DNA molecules are well separated, a constric=on
forms at the midpoint of the cell (as seen in step 5)
▪ (As seen in step 6) A new membrane and cell wall are
synthesized at the site of constric=on
• FtsZ: The protein this gene encodes forms a ring at the site of
constric=on where the new cell wall forms between the two daughter
cells; Present in the genomes of many bacteria and archaeons
◦ Evolu=onarily related to tubulin, which makes up the dynamic
microtubules found in eukaryo=c cells that are needed in
intracellular transport, cell movement and cell division
11.1.2 Eukaryo7c cells reproduce by mito7c cell division.
• Instead of the single and small circular DNA molecules that is the
genome of prokaryotes, the genome of eukaryotes is typically much
larger and organized into 1/+ linear chromosomes
• DNA of prokaryotes is abached to the inside of the plasma membrane,
allowing separa=on of replicated DNA into daughter cells by cell growth
BUT, the DNA of eukaryotes is located in the nucleus so, cell division
must first involve the breakdown and re-forma=on of the nuclear
envelope and mechanisms other than cell growth to separate replicated
DNA (the chromosomes of dividing eukaryo=c cells abach to the mito=c
spindle, which separates them into daughter cells)
• Some unicellular eukaryotes exhibit forms of cell division that have
characteris=cs of binary fission and mitosis
◦ Example: Dinoflagellates (Evidence to suggest mitosis evolved
from binary fission)
• Have a nucleus and linear chromosomes
• Nuclear envelope doesn't break down but stays intact
during cell division
• Replicated DNA is abached to the nuclear envelope
• Nucleus then grows and divides in a way like binary fission
11.1 Cell Division
• The process by which a single cell becomes two daughter cells
• Requirements of cell division:
◦ Two daughter cells must each receive the full complement of
gene=c material (DNA) present in the parent cell
◦ Parent cell must be large enough to divide in two and s=ll
contribute sufficient cytoplasmic components (like proteins, lipids,
etc.) to each daughter cell
• So, cellular components must be duplicated before cell
division occurs
• Prokaryo=c cells divide by binary fission
• Eukaryo=c cells first divide the nucleus during mitosis and then, divide
the cytoplasm into two daughter cells during cytokinesis
◦ Note: Adult stem cells can only replace non-reproducing
specialized cells
• Example: When skeletal muscle is damaged, quiescent (i.e.
non-dividing) satellite stem cells present in the basement
membrane of the muscle =ssue are ac=vated from their
dormant G0 phase and begin to divide to enable muscle
regenera=on
▪ Ac=va=on of satellite stem cells leads to prolifera=on,
differen=a=on and fusion of muscle precursor cells
(i.e. myoblasts) which become the muscle cells of the
myofibers
◦ Mitosis likely evolved from binary fission
11.1.1 Prokaryo7c cells reproduce by binary fission.
• Bacteria, archaeons, chloroplasts and mitochondria divide by binary
fission
• Binary Fission: A cell replicates its DNA, increase in size, and divides into
two daughter cells
, ◦ As determined by studying E. coli:
▪ Just aWer step 4, when the cell is ~2x its size and the
DNA molecules are well separated, a constric=on
forms at the midpoint of the cell (as seen in step 5)
▪ (As seen in step 6) A new membrane and cell wall are
synthesized at the site of constric=on
• FtsZ: The protein this gene encodes forms a ring at the site of
constric=on where the new cell wall forms between the two daughter
cells; Present in the genomes of many bacteria and archaeons
◦ Evolu=onarily related to tubulin, which makes up the dynamic
microtubules found in eukaryo=c cells that are needed in
intracellular transport, cell movement and cell division
11.1.2 Eukaryo7c cells reproduce by mito7c cell division.
• Instead of the single and small circular DNA molecules that is the
genome of prokaryotes, the genome of eukaryotes is typically much
larger and organized into 1/+ linear chromosomes
• DNA of prokaryotes is abached to the inside of the plasma membrane,
allowing separa=on of replicated DNA into daughter cells by cell growth
BUT, the DNA of eukaryotes is located in the nucleus so, cell division
must first involve the breakdown and re-forma=on of the nuclear
envelope and mechanisms other than cell growth to separate replicated
DNA (the chromosomes of dividing eukaryo=c cells abach to the mito=c
spindle, which separates them into daughter cells)
• Some unicellular eukaryotes exhibit forms of cell division that have
characteris=cs of binary fission and mitosis
◦ Example: Dinoflagellates (Evidence to suggest mitosis evolved
from binary fission)
• Have a nucleus and linear chromosomes
• Nuclear envelope doesn't break down but stays intact
during cell division
• Replicated DNA is abached to the nuclear envelope
• Nucleus then grows and divides in a way like binary fission
