Download Cell Cycle-Binary Fission, Regulation

Cell Cycle: Binary Fission, Regulation and Cancer
Bacteria and Binary Fission
• Prokaryotes reproduce by binary fission
• As the chromosome is replicated the copied regions move to the opposite ends of cell.
• The bacteria grows until it reaches 2x its original size.
• Fission only allows bacteria to produce identical copies, which leaves them vulnerable
to being wiped out.
• They do have ways to achieve genetic differences, however.
• Some bacteria can transfer DNA to another bacteria and some can take up DNA from
their environments.
Regulation of cell cycle
• Some cells divide frequently in life (skin cells), and others can divide not as frequently,
(reserve - liver cells) mature nerve and muscle cells do not divide at all.
Checkpoints
• G1 checkpoint is the most important.
• At this point, the cell either gets the go ahead to finish cycle and divide, or receives a
stop signal.
• If it is a stop signal, it goes into G0 phase (on “pause”).
• Most human cells are in this mode.
• There are 2 other checkpoints that the cell must pass through.
• The G2 checkpoint determines if the cell can continue on to mitosis.
• The M checkpoint happens in the middle of mitosis; it makes sure the chromosomes
are going to divide correctly.
Cancer
• Cancer cells divide out of control.
• Some cancers can produce their own growth factors and some have a problem in
signaling pathway (they donʼt know when to stop).
• Cells can divide indefinitely if they have enough nutrients.
• If the immune system does not destroy the cancer cell, it can form a tumor (gathering
of cells).
• If tumor does not invade other areas, it is benign.
• If it does, it is malignant.
• If the cells get into the blood stream, it can travel throughout the body (metastasis).