Download Cell grows in size

Chapter – 8
The Cellular Basis of Reproduction & Inheritance
– Mitosis
1
Outline

The Cell Cycle

Interphase

Mitotic Stage

Cell Cycle Control

Apoptosis

Mitosis & Cytokinesis

Mitosis in Animal Cells

The Cell Cycle & Cancer

Prokaryotic Cell Division
2
The Cell Cycle

An orderly set of stages.

The two major stages of the cell cycle:
a. Interphase

The cell grows larger

The number of organelles doubles

The DNA is replicated
b. Mitosis and Cytokinesis
3
The Cell Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Interphase
G1 checkpoint
Cell cycle main checkpoint.
If DNA is damaged, apoptosis
will occur. Otherwise, the cell
is committed to divide when
growth signals are present
and nutrients are available.
S
(growth and DNA
replication)
G1
G0
G1
(growth)
M
G2
(growth and final
preparations for
G2
division)
G2 checkpoint
Mitosis checkpoint.
Mitosis will occur
if DNA has
replicated properly.
Apoptosis will
occur if the DNA is
damaged and
cannot be repaired.
M
M checkpoint
Spindle assembly
checkpoint. Mitosis
will not continue if
chromosomes are
not properly aligned.
4
Animation
Please note that due to differing
operating systems, some animations
will not appear until the presentation is
viewed in Presentation Mode (Slide
Show view). You may see blank slides
in the “Normal” or “Slide Sorter” views.
All animations will appear after viewing
in Presentation Mode and playing each
animation. Most animations will require
the latest version of the Flash Player,
which is available at
http://get.adobe.com/flashplayer.
Animation
Please note that due to differing
operating systems, some animations
will not appear until the presentation is
viewed in Presentation Mode (Slide
Show view). You may see blank slides
in the “Normal” or “Slide Sorter” views.
All animations will appear after viewing
in Presentation Mode and playing each
animation. Most animations will require
the latest version of the Flash Player,
which is available at
http://get.adobe.com/flashplayer.
6
Interphase consists of: G1, S and G2 phases

G1 Phase:



S Phase:



Cell doubles its organelles
Cell grows in size
DNA replication
Chromosomes leave with 2 identical chromatids each
G2 Phase:


Cell grows in size and
prepares for mitosis
7
Mitotic (M) Stage

Includes:


Nuclear division (karyokinesis)

Daughter chromosomes distributed to two daughter
nuclei
Cytokinesis

Cytoplasm division

Results in two genetically identical daughter cells
8
Mitosis: Preparation

DNA is in very long threads
 Chromosomes
 Stretched out and intertangled between divisions
 DNA is associated with histone proteins
 Collectively called ‘chromatin’.
9

Before mitosis begins:

Chromatin condenses (coils) into distinctly visible
chromosomes

Each species has a characteristic chromosome
number



Humans 46
Corn 20
Goldfish 94
10
Animation
Please note that due to differing
operating systems, some animations
will not appear until the presentation is
viewed in Presentation Mode (Slide
Show view). You may see blank slides
in the “Normal” or “Slide Sorter” views.
All animations will appear after viewing
in Presentation Mode and playing each
animation. Most animations will require
the latest version of the Flash Player,
which is available at
http://get.adobe.com/flashplayer.
Chromosome Number
Diploid (2n) number includes two sets of
chromosomes. Humans have 23 pair of
chromosomes in each body cell, making a
total of 46 in each nucleus. One set of 23 is
coming from father (paternal) and other set of 23
Is coming from mother (maternal).
Haploid (n) number include one set of
chromosome. Only sperm and eggs have 23
chromosomes (haploid set).
12
A karyotype is an organized profile of a person's
chromosomes. In a karyotype, chromosomes are arranged
by size, from largest to smallest.
An autosome is a non- sex chromosome. For example, in
human, there are twenty-two pairs of autosomes, and a pair
of sex chromosomes (XX or XY).
13
Chromosome Numbers of Some Eukaryotes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
14
Chromosome Structure

At end of S phase:
 Each chromosome internally duplicated
 Consists of two identical DNA chains
 Sister chromatids (two strands of genetically identical
chromosomes)
 Attached together at a single point (called centromere)
15
Mitosis in Animal Cells

Just outside nucleus is the centrosome. (This is the
microtubule organizing center).
 In animals, it contains two barrel-shaped centrioles,
oriented at right angles to each other and each composed
of a bundle of microtubules.
 Centrosome will be replicated in S-phase, resulting in two
centrosomes. Just before mitosis, the two centrosomes
move apart until they are on opposite sides of the nucleus.
16
Mitosis in Animals and Plants
17
Mitosis in Animal Cells: Prophase

Two sister chromatids attached at centromere are clearly
visible.

Nucleolus disappears

Nuclear envelope disintegrates

Centriole will produce spindle fibers or the mitotic
spindles. Microtubules grow out from each centrosome
with their ends growing toward the metaphase plate.
These clusters of microtubules are called spindle fibers.
18
Mitosis in Animal Cells: Prometaphase
Centromere of each chromosome develops
two kinetochores, specialized protein complex,
over each sister chromatid, they physically
hook sister chromatids with microtubules.
19
Mitosis in Animal Cells: Metaphase
Chromosomes, (made up of sister chromatids), are
pulled around by kinetochore (spindle) fibers and
forced to align across equatorial plane (metaphase
plate) of cell.
20
Mitosis in Animal Cells: Anaphase
Centromere breaks in the middle, releasing sister
chromatids. Sister chromatids separate and are pulled to
Opposite poles by the contraction of the spindle fiber.
Each sister chromatid is now called daughter
chromosomes.
21
Mitosis in Animal Cells: Telophase
Spindle disappears.
Two clusters of chromosomes are resulted.
Around each cluster, nuclear envelopes form.
Chromosomes uncoil and become chromatin again.
Nucleolus reappears
Resulting in two daughter nuclei inside a parent cell.
22
Cytokinesis: Animal Cells
Division of mother cell’s cytoplasm into two. Often begins in
anaphase
Animal cytokinesis:



A cleavage furrow appears between daughter nuclei
(Formed by a contractile ring of actin filaments)
Eventually pinches mother cell in two
23
Cytokinesis: Plant Cells – Cell Plate formation
Many small membrane-bounded vesicles are formed in the middle of
the parent cell and they extend towards the periphery. Vesicles fuse to
form a cell plate. The membranes of the cell plate become the plasma
membrane between the daughter cells. Contents of vesicles become the
middle lamella between the two daughter cells. On opposite sides of
middle lamella, daughter cells later secrete primary cell walls.
24
Function of Mitosis




Permits growth and repair.
Allows a cut to heal or a broken bone to mend
In plants, it helps to divide throughout the life of the
plant.
In mammals, mitosis is necessary for embryo becomes
a fetus
25
The Cell Cycle and Cancer

Abnormal growth of cells is called a neoplasm
 Benign neoplasms are not cancerous
 Do not invade neighboring tissue or spread
 Malignant neoplasms are cancerous
 Readily invade neighboring tissues
 development of cancer (carcinogenesis) is gradual,
may take years before cell becomes cancerous
26
Characteristics of Cancer Cells

Lack differentiation
 Have abnormal nuclei
 Form tumors
27
Prokaryotic Cell Division - Binary fission
(Asexual Reproduction)
Prokaryotic cell contains a ring shaped DNA in nucleoid
region; DNA attaches to the plasma membrane; DNA
replicates into two rings; Replicated 2 DNA rings migrate
towards opposite poles; Formation of septum between the 2
replicated DNA, dividing the parent cell; Produces two
daughter cells identical to original cell.
28
Review

The Cell Cycle

Interphase

Mitotic Stage

Cytokinesis

Mitosis in Animal cells and Plant cells

The Cell Cycle & Cancer

Prokaryotic Cell Division
29
30