Download 2.3 Cell Division

The sequence of growth and division
cells undergo
 3 main stages
 Parent cell divides to form two identical
daughter cells

Period before cell division occurs
 Longest stage
 Has three components


Growth
› Cell doubles in size
› Produces structures needed to carry out its
functions

DNA Replication
› Replication a process in which the cell
makes a copy of it’s DNA in the nucleus
› At the end of this part, a cell has two
identical copies of DNA

Preparation for Division
› Cell produces structures needed during
division
Stage during which cell’s nucleus divides
into 2 new nuclei
 Has four phases

› Prophase, metaphase, anaphase, and
telophase
Chromatin begins to condense and coil
into tiny rods
 Since the DNA has replicated, each rod
is doubled
 Chromosome doubled rod of
condensed chromatin
 Chromatid one strand of the
chromosome
 Centromere structure holding the two
strands of the chromosome together


Chromosomes line up across the center
of the cell and attach to spindle fiber at
the centromere
Centromeres split
 Chromatids separate and move to
opposite ends of cell

Chromosomes lose their rod like
appearance
 Nuclear membrane forms around each
region of chromosomes

Final stage in the cell cycle
 Cytoplasm divides
 Organelles are distributed into the 2 new
cells
 Each daughter cell has the same
number of chromosomes as the parent
cell
 Cell enters interphase and cycle begins
again!

Depends on type of cell
 Length of each stage also varies
 Human brain cells never divide

› They get larger and they make more
connections
› Full size at age 6
DNA looks like a twisted ladder
 Called a double helix
 Each rung is made up of molecules
called nitrogen bases
 Adenine pairs with thymine
 Guanine pairs with cytosine

The 2 sides of DNA unwind and separate
 Separates between base pairs
 Nitrogen bases floating in nucleus pair
up with base on each side
 The produces two identical copies of
DNA
