Transcript Cell Division

Cell Division
Objectives
1. Describe the cell cycle.
2. Describe the events in each stage of
mitosis.
3. Explain cancer as a disease of the cell
cycle.
Pg 240-252
Think! Think!! Think!!!
Does a living thing grow larger
because it increases the size of its
cells or because it produces more
cells?
Think! Think!! Think!!!
Living things grow because they produce more
cells.
There is a limit to the size that cells can grow.
The DNA that is in the nucleus of each cell is like
the library of a small town. When the town is
small, there are enough books for the residents to
share. If the town population were to increase,
there would be a shortage of books.
So instead of growing larger, cells must reproduce.
Cell Division
Cell Division – the process by which a cell
divides into two new identical daughter
cells
Before cell division, the DNA of the cell is
copied, so each daughter cell gets a copy.
DNA – (deoxyribonucleic acid) the large
molecule in the nucleus of each cell that
carries genetic information
Chromatin
Chromatin - DNA in the nucleus that looks
like spread out “strings” when the cell is not
dividing
Chromosomes
Chromosomes – condensed chromatin
visible in the nucleus when the cell is
dividing
Humans have 46 chromosomes or 23 pairs.
Chromosomes
Before cell division, each chromosome is
duplicated. The identical chromosomes attach to
each other.
Sister Chromatids –
two identical chromosomes
attached to each other
Centromere – the place
that the sister chromatids
are attached to each other
The Cell Cycle
Interphase
 G1 – “G for Grow” the cell
size increases
 S – “S for DNA Synthesis”
the chromosomes are
duplicated
 G2 – centrioles and other
organelles required for cell
division are made
Mitosis – the duplicated
chromosomes separate, has four
phases
Cytokinesis – the cell physically
splits in two
Cancer: A Disease of the Cell
Cycle
Cancer – a disorder in which some of the
body’s cells divide uncontrollably.
The cells that continue to divide cause
masses called tumors.
Causes can be tobacco, UV radiation, or
viruses.
Mitosis
Prophase – chromatin condenses
into sister chromatids, centrioles
separate, spindle forms, nuclear
envelope breaks down
Metaphase – sister chromatids line
up across middle of cell, each is
connected to a spindle fiber at its
centromere
Anaphase – sister chromatids
separate and move to opposite sides
of the cell
Telophase – sister chromatids lose
their shape and become chromatin,
two new nuclear envelopes form
http://www.rattlerscie
nce.com/life/classes/p
reapbio/documents/U
nit%203/chapter10/ce
ll_cycle.swf
http://bio.rutgers.edu/
~gb101/lab2_mitosis/
graphics/aavideo.mov