Download mitosis

Cell Division and Reproduction
• Before a cell becomes too large, it divides
forming 2 “daughter” cells. This process is
called cell division.
• It keeps the large SA:V and keeps the cell from
having “information overload” by coping its
genetic material
Reproduction
• Asexual: the production of genetically
identical offspring from a single parent Ex:
bacteria, hydra, some plants
• Sexual: offspring produced by sexual
reproduction inherit some of their genetic
information by each parent Ex: most animals
and plants
Cell Cycle
• Chromosomes- Genetic information (DNA)
bundled in to packages
– In most prokaryotes, a single chromosome holds
most of the organism's DNA
• Eukaryotes usually have much more DNA
• Chromosomes in eukaryotic cells form a close
association with histones, a type of protein.
• Chromosome + histone= chromatin
• Centrioles- organelle used to pull apart
chromosomes
• Spindle fibers- fibers used to pull apart
chromosomes
• Cell cycle: cells grow, prepare for division and
divides to form 2 daughter cells
• Prokaryotic Cell Cycle: Binary Fission (asexual)
– DNA duplicates, cell membrane indents, cell divides,
2 new cells with genetically identical organisms are
produced
Eukaryotic Cell Cycle
• Interphase: Resting stage of cycle; DNA is
copied
Interphase
• G1 Phase: Cell Growth
• S Phase: DNA replication
• G2 Phase: Preparation for mitosis
• M Phase: follows interphase, produces 2
daughter cells
Prophase
• The DNA condenses into visible chromosomes
• The nuclear envelope disappears
• Spindle fibers form
Metaphase
• Chromosomes align at the center of the cell
• Spindle fibers connect the centromere of each
chromosome to the two poles of the spindle
Anaphase
• The sister chromatids pulled apart by spindle
Telophase
• Chromatids are at opposite ends of cell
• Nuclear envelope reforms
• Spindle disappears, chromosomes disappear
Cytokinesis
• The cytoplasm divides into two cells. Each cell
is identical to the parent cell
• Mitosis- the nucleus divides
• Cytokinesis- the cytoplasm divides
• Cytokinesis in plant cells: cell wall is too ridged
to bend so a cell plate forms and later
becomes the cell membranes followed by the
new cell wall
Regulating the Cell Cycle
• The cell cycle is controlled by regulator
proteins both inside and outside the cell
• Cyclin: a protein that regulates the cell cycle
• Internal regulators: respond to events within
the cell
– Ex: proteins that make sure a cell does not enter
mitosis until its chromosomes have replicated
• External regulators: respond to events outside
the cell
– Ex: Growth factors stimulate the growth and
division of cells
• Apoptosis: Programmed Cell Death
Cancer: uncontrolled cell growth
• Cancer cells do not respond to signals that
regulate the growth of most cells.
• Could be caused by defects in the genes that
regulate cell growth and divisions
• Sources of such defects include: smoking or
chewing tobacco, radiation exposure, other
defective genes