Transcript Mitosis PPT - Roslyn Public Schools

Mitosis

Purpose: occurs in
somatic (body) cells
for growth and
repair of tissue (ex.
Growing, or healing
an injury). Occurs in
both plants and
animals: asexual
reproduction,
(starting a new plant
from a stem/leaf of
another one)
 Method:
mitosis involves
one duplication of
nuclear material, and one
division of the cell.
Chromosome number is
maintained (diploid 
diploid (normal
chromosome #).
 Daughter
cells are
identical to each other
and to the parent cell.
The cellular life cycle
Cell Cycle:

Interphase – mostly the active growth and
metabolism of the cell, but at the end of
interphase, DNA (found in chromosomes)
duplicates (makes a copy of itself)

During interphase, chromosomes are referred to
as chromatin – a loosely scattered arrangement
of chromosomes
Mitotic Phase

Period of cell division

Shortest stage in the cell
cycle
Chromosomes Vs. Chromatin

DNA exists in Chromatin
form in the nucleus.

The chromatin condenses
to form Chromosomes
during cell division

INTERPHASE: The normal
growth and development
stage of cells

During this stage cellular
activities proceed normally

There is no DNA replication

Cell produces proteins
through protein synthesis

Cells usually increase in size
and mass

Chromosomes are not
readily visible and are
intertwined in the nucleus

This is known as the “G1 stage” of the cellular cycle. The
cell spends the majority of its life in this stage.

The cell then enters the “S” or Synthesis stage. During this
stage of Interphase DNA replication occurs and the
chromosomes make identical copies of themselves.

The “G2 stage” is a short period of growth and other
preparations necessary for mitosis.
Interphase in an animal cell
PROPHASE: At the end
of Interphase the
chromosomes
replicate themselves.
This signals the start of
prophase
 During prophase the
centrioles migrate to
opposite poles of the
cell
 The nuclear
membrane breaks
down and dissolves
 The chromosomes
shorten & thicken

Prophase in a plant cell
Prophase in an animal cell

At this point the two replicas of the parent chromosomes are
called chromatids

The two chromatids are joined together in a region known as the
centromere

As prophase continues some of the cells cytoskeleton (made up
of microfilaments) form the spindle fibers

By the end of prophase an entire network of microfilaments has
formed and is attached to the chromatids at the centromere

The cell now enters METAPHASE
 Metaphase
begins
as the chromatids
begin to move
towards the
equator of the cell
 When all the
chromatids have
reached the
center of the cell
AND begin to
separate
ANAPHASE begins
Metaphase in an animal cell
Metaphase in a plant cell
What
differences can you
describe between the 1st
Meiotic metaphase and the
metaphase in mitosis?
What
differences can you
describe between the 2nd
Meiotic metaphase and the
metaphase in mitosis?

Anaphase begins with the
separation of chromatid
pairs

Once separated each
chromatid is called a
chromosomes

By late anaphase an
equal number of
chromosomes has
reached each pole

The cell membrane begins
to change shape getting
thinner in the middle
Anaphase in an animal cell
Anaphase in a plant cell
Telophase: during
early telophase the
chromosomes uncoil
 The fragments of the
nuclear membrane
begin to reassemble
around the
chromosomes
 The nucleolus
reappears
 The cell membrane,
and cell plate in plant
cells, begins to form in
the space between
the two new nuclei.

Telophase in an animal cell
Telophase in a plant cell

The two daughter cells separate
by a process called cytokinesis

The cell membrane returns to
normal and the new daughter
cells enter Interphase

And the cycle continues…..
Vocab Words