Download CELL REPRODUCTION: MITOSIS

CELL
REPRODUCTION:
MITOSIS
Cell division
• Cell reproduction: the process of one cell
dividing into two cells
parent cell  two daughter cells
• Mitosis: asexual reproduction to make new
cells for organism growth or tissue repair
*25 million cells undergoing mitosis each
second in the human body
Spontaneous Generation & the Theory of Biogenesis
• The now disproved idea that living things
arose from non-living things.
ex: spoiled meat “growing” maggots
• Disproved eventually by Louis Pasteur (see page 177-178)
• The Theory of Biogenesis: all life come from
life; so...all cells come from other cells
Cell Division
• Basics:
Asexual reproduction – cells duplicate their DNA
and split into two genetically identical cells
ex: mitosis, budding, binary fission
*all multicellular organisms perform mitosis
Sexual reproduction – a combination of genetic
material from two different organisms resulting
in an offspring that is genetically different than
the parent
ex: meiosis
Cell Life Cycle
• Phases:
1. interphase: where the cell spends 90% of their
lives
2. prophase
3. prometaphase
4. metaphase
5. anaphase
6. telophase
*PPMAT = phases of mitosis (#2-6)
DNA Replication
• Occurs at the end of interphase
• Helicase unzips the DNA strand
• DNA polymerase binds to the DNA strand and
creates a complementary daughter strand
• This creates two new strands of DNA (p. 182)
• After DNA replication the cell enters mitosis
• The identical strands of DNA (which are called
sister chromatids) are held together in the
middle by the centromere
Interphase
•
•
•
•
spends most of its life (time) in this phase
performs everyday vital functions
DNA in the form of chromatin
during the end of interphase the cell replicates the
DNA (46 chromosomes becomes 92 – two exact
copies of each)
Prophase
• the nucleoli begin to disappear
• DNA condenses and becomes visible
• the spindle has formed and extends from the
centrioles
• chromosomes are visible as two sister chromatids
held together at the centromere
Prometaphase
• also called late prophase or early metaphase
• nuclear membrane disintegrates
• the spindle attaches to centromere of each
pair of sister chromatids
Metaphase
• the chromosomes line up completely along
the equator of the cell
Anaphase
• the spindle fibers contract and pull the sister
chromatids apart, toward opposite ends of the cell
• karyokinesis – the process of the chromosomes
being pulled apart
Telophase
• nuclear membrane begins to reform around the
chromosomes
• the chromosomes relax and unwind, take the form of
chromatin
• two cells form
• cytokinesis – the process of the cell pinching inward
and forming two cells
Plant cell division
• since the plant cell has a rigid cell wall it
cannot pinch inward to form 2 new cells
• the two daughter cells form inside
• a cell plate forms from the
Golgi or ER at the center of
the cell which forms into a
new cell wall