Cell Unit
LT #3 I can DESCRIBE how cells
multiply.
Sam’S PuPPy
• Body cell reproduction involves producing
new daughter cells for growth of tissues as
well as repair and replacement of old cells.
• Most living body cells eventually divide
into two cells through a process called
mitosis. This can happen because food and
nutrients are broken down and become
building blocks for new living materials like
the new cells produced during cell
division.
Why do cells divide?
• Weeds can grow pretty fast. In fact,
the stems and roots of a fastgrowing plant seem to get longer
over night. Where do the new stem
and root parts come from?
– They are made when existing cells
divide to form new cells. This process
is called cell division.
Why do cells divide?
• Eventually cells need to duplicate.
There are two types of cell
division, mitosis (growth) and
meiosis (reproduction).
• Mitosis allows organisms to grow
larger, and also helps organisms
replace injured cells. GROWTH!
Mitosis
• The big idea to remember is that
mitosis is the simple duplication of a
cell and all of its parts.
• It duplicates its DNA and the two new
cells (daughter cells: cells resulting from
the replication and division of a single
parent cell) have the same pieces and
genetic code.
Two identical copies come from one
original. Start with one; get two that
are the same. Get the idea?
Mitosis
• Before a eukaryotic cell (a cell with
an organized nucleus) divides, the
genetic material in the nucleus of
the cell copies itself.
• When the cell divides, the nuclear
material splits in half so that each
daughter cell gets genetic material
that is the same as that of the
parent cell.
Mitosis
• The dividing of the nuclear
material is known as mitosis.
• In the last stage of cell division,
the cytoplasm divides as well.
• There are now two complete
cells where there used to be
one.
Science Alert!
• The terms mitosis and cell division
are sometimes used
interchangeably.
• BUT…mitosis really refers only to
the dividing of the nuclear material.
• While…cell division is the complete
process of copying and dividing the
whole cell.
Cell Division Phases
• Beyond the idea that two identical
cells are created, there are
predictable stages or phases in the
cell division process.
• These steps ensure that the new
daughter cells are the same as the
cell from which they formed.
Cell Division
• There are 5 basic phases in the lifecycle of a cell.
–Interphase
–Prophase
–Metaphase
–Anaphase
–Telophase
Cell Division Video of a Animal Cell
Cell Division
• The following mnemonic devices can
help you remember the phases of cell
division.
• I prefer milk and tea.
• I propose meeting at ten.
• In Poland men are tall.
• CAN YOU COME UP WITH YOUR OWN
mnemonic device?
Cell Division/Mitosis
• Interphase
– The stage before cell division starts.
– As a cell prepares to divide, each
chromosome in the nucleus makes an
exact copy of itself.
– Chromosomes: a structure made of DNA that
contains the genetic info used to direct cell activity
and make new cells
Cell Division/Mitosis
• Prophase
– The nucleus prepares for cell division.
– The genetic material shortens and
thickens.
– The chromosome copies are held
together at their centers, so they form a
sort of “X.”
Cell Division/Mitosis
• Metaphase
– The two copies of each chromosome
line up in the center of the cell.
Cell Division/Mitosis
• Anaphase
– The copies separate.
– One complete set of chromosomes is
pulled to one side of the cell.
– The other complete set is pulled to the
other side of the cell.
Cell Division
• Telophase
– Final stage of cell division
– The cytoplasm pinches in at the
center of the cell, dividing the cell in
half.
– When cell division is complete, two
new daughter cells are formed.
– The daughter cells are identical to
the parent cell.
Cell Division-Mitosis Stages-Video
Two identical copies come from one
original. Start with one; get two that
are the same. Get the idea?
Bellringer
Please take a graphing
worksheet and your
cursive practice from the
wooden table and
complete silently at your
desk.