Transcript Biology I 1/5/07 Cell Division & Chromosomes

Cell Growth
• Before a cell gets too large, it divides
forming two “daughter” cells.
Cell Division- the process by which a cell divides
into two new daughter cells
• A cell must copy its genetic information
before cell division begins
• Each daughter cell then gets a complete
copy of that information.
Types of Reproduction
•Asexual
reproduction
•Sexual
reproduction
Asexual Reproduction
• Binary fission
• Budding
• Vegetative propagation
Binary fission
• In prokaryotes (bacteria), one cell
divides to form two identical cells.
• The cells are the same size and carry
the same genetic information.
Budding
• Similar to binary fission except
the cytoplasm divides unequally.
• The result is two cells with the
same genetic information, but one
is larger than the other.
• E.g. Yeast cells
Vegetative Propagation
• Occurs in plants
• Complete new plants develop
from parts of the parent
plant, such as the root, stem
and leaf
• E.g. Potatoes
• All cells come from other cells by cell
division.
• For living things to grow and repair,
their cells must divide over and over
again.
• In a cell containing a nucleus, the
nucleus and cytoplasm divide by
separate processes.
• Division of the nucleus through a
series of events is called mitosis.
• In eukaryotes, cell division occurs in two
main stages
» - mitosis- the division of the
nucleus
»- cytokinesis- the division of the
cytoplasm
Cell Cycle
• A series of events cells go
through as they grow and
divide.
During the cell cycle, a cell grows,
prepares for division, and divides to
form two daughter cells. Each daughter
cell then begins the cycle again.
The phases of the cell cycle include
interphase and cell division.
• Interphase is divided into three phases:
G1, S, and G2
– During the G1 phase- Cells increase in size
and make new proteins and organelles
– In the S phase- the copying of chromosomes
take place
– During the G2 phase- many of the organelles
and molecules needed for cell division are
produced.
• So what does the M stand
for?
http://www.sci.sdsu.edu/multimedia/mitosis/anim_samples.html
Wrap-Up
• When a cell makes an
exact copy of its DNA
it is called?
Warm-Up 1/28/08
Justify your answer!
Which statement describes the major role of
lipids within a cell?
A. They cause DNA to replicate.
B. They move RNA in the cytoplasm.
C. They catalyze chemical reactions in
the cell cytoplasm.
D. They are the main structural
components of membranes.
Mitosis and Cytokinesis
• Biologists divide the events of
mitosis into four phases:
Prophase, metaphase,
Anaphase and telophase.
http://nobelprize.org/educational_games/medicine/2001/
Interphase
Prophase
Pro=
before
http://www.sci.sdsu.edu/multimedia/mitosis/anim_samples.html
• Chromosomes condense and become
visible
• Centrioles separate and move to opposite
poles
• Chromosomes attach to fibers in the
spindle
• Nuclear envelop breaks down
Metaphase
Meta- = middle
• Chromosomes line up across the center of
the cell
Anaphase
ana- = back
• The centromeres joining sister chromatids
split. The sister chromatids become
individual chromosomes. The two sets of
chromosomes move apart.
Telophase
telo- = end
• Chromosomes move to opposite ends of
the cell.
• They lose their distinct shapes.
• Two new nuclear envelops form.
Cytokinesis
-kinesis = movement
• Occurs at the same time as telophase.
• In most animal cells, the cell membrane
pinches the cytoplasm into two nearly
equal parts.