4. Why produce identical cells?
• Somatic cells contains 2 sets of chromosomes,
maternal and paternal = diploid, 2n
• Gametes (sperm and ovum) have only
__one_________ set of unpaired chromosomes
= haploid, n
• Each organisms has its own fixed number of
chromosomes, e.g. human has 46 chromosomes
(23 pairs).
• Producing identical cells preserves the
___original genetic________ number
of chromosomes.
5. Significance of mitosis
• Produces new cells for growth, repair and
replace damaged or dead cells.
• Forms asexual reproduction in unicellular
organisms.
• Ensures new cells are ____identical______ to
parent cells.
• Preserves the ___diploid________ number of
chromosomes of species.
6. The Cell Cycle
Series of cellular
Interphase
reproductive events in
which duplication of
cell content and cell
division occur in an
orderly sequence G1
S
Cytokinesis
telophase
anaphase
Mitosis G2
metaphase
prophase
Mitotic (M) phase
7. Cell Cycle
• Consist of 2 major phases:
Phase 1: Interphase
Phase 2: Mitotic phase (M phase)
• Interphase involves ___stages/phases________
for cell division
– It has 4 subphases: G0 G1, S, G2
– G1, G2: cell growth, produce proteins and organelles,
cell differentiation
– S: synthesis of DNA, duplication of chromosomes
and replication of DNA
• M phase, the cell divides
– Includes mitosis (nuclear division) and cytokinesis
(cytoplasmic division)
8. • Chromosomes are ___copied________ (#
doubles)
• Chromosomes appear as threadlike coils
____chromatin_______ at the start
Cell membrane
Nucleus
Cytoplasm
11. • Chromosomes condense
• Centrioles (or poles) appear and begin to move to
__opposite_________ end of the cell.
• Nuclear membrane disappear
• Nucleolus disappear
• Spindle fibers form between the poles.
Centrioles
Sister
chromatids
Spindle fibers
13. • Chromatids (or pairs of chromosomes)
attach to the spindle fibers, line up on equator
• Each chromatid face __opposite_________
poles
• End when centromere divides
Centrioles
Spindle fibers
15. • Chromatids (or pairs of chromosomes)
separate and begin to move to opposite ends
of the cell.
• Shortening of spindle fibre
• Chromatids chromosomes (daughter)
Centrioles
Spindle fibers
17. • Two new nuclei form.
• Chromosomes appear as chromatin (threads
rather than rods).
• 2 sets of chromosomes one at
each__end_______
• Spindle fibres disappear
• Nucleolus & nuclear membrane are formed
• Mitosis ends. Nuclei
Nuclei
Chromatin
19. • Cell membrane moves inward (constrict) around
the __cytoplasm_________ of cell to create two
daughter cells – each with its own nucleus with
identical chromosomes.
21. CYTOKINESIS (PLANT)
• In plant cells, cytokinesis starts with formation of cell
plate at the ___________ of cell
• Cell plate enlarges until it ___________ with plasma
membrane
• New cell wall is produced and separates the two
daughter cells
24. MITOSIS
ANIMAL PLANT
Similarities:
Two identical cells are formed at the end of a division
They produce more cells and cause growth
Differences:
Centrioles found at each pole No centrioles
during mitosis (cortical microtubules)
Mainly localized in special
regions called meristems to
Cells divide everywhere, all
either elongate the tips of
the time
stems and roots or expand
the girth of the plant
Formation of cleavage furrow Formation of cell plate that
at the equatorial plane grow outwards
25. REGULATION OF CELL CYCLE
• The cell cycle is
controlled by
___regulatory__
proteins __ in
the cytoplasm
• Each type of cell
has its own timing
• Some has
frequent division
26. Controlled Mitosis
• The ability of cell to divide at its own timing and
rate
• Enables __normal_________ growth and
development and maintenance for perpetuity of
living things
27. Uncontrolled Mitosis
• If the genes that regulate the cell cycle are
damaged or mutated, cell divide
__abnormal___cell growth_____
• Cause:
– Harmful ray: nuclear radiation, UV ray
– Viruses
– Carcinogenic chemicals: food additives, benzo (α)
pyrene in cigarette smoke
28. The Effects of Uncontrolled Mitosis
• Unregulated and very fast
division increase the
number of abnormal cells
• Form an abnormal mass –
tumour
• Types of tumour:
Brain
– Malignant
cancer
• Invasive by
metastasis Breast
• Cancer cancer
– Benign
• Localize What is the treatment of
• Does not cause cancer?
serious problems
• Remove by
___________
29. Mitosis Application: CLONING
• The process to produce genetically identical
cells / tissues / organisms / population from the
mitosis of a single parent cell (clone)
• Naturally: asexual reproduction, vegetative
propagation (plant)
• Artificially: cloning (animal), tissue culture (plant)
Why?
– Increase quantity
– Improve quality
– Ensure uniformity of traits
30. Animal Cloning
Cloning is carried
out by replacing
nucleus of an
_________donor__
___ egg cell with the
nucleus of a diploid
cell
31. ADVANTAGES OF CLONING
• rapid multiplication, mass production in short
time
• genetically identical, desirable traits inherited
and propagated
• therapeutic cloning, replace damaged or
diseased tissues / organs
• fetal cell cloning, early detection of genetic
defects
• no seeds / difficult to germinate, propagate
endangered or rare species
32. DISADVANTAGES OF CLONING
• no genetic variation, susceptible to changes and
new diseases, extinction
• possibility of mutations, harmful effects of GMF
• grow old quickly, shorter lifespan
• exclusion of certain species, decrease
biodiversity
• traits transfer to wild species, creation of
superweeds
34. What is Meiosis?
• Meiosis produces daughter cells that have
one half the number of chromosomes as the
parent cell.
• Meiosis enables organisms to reproduce
sexually.
• Meiosis involves two divisions producing a
total of four daughter cells.
35. Summary of the Phases of Meiosis
• meiosis 1: prophase 1, metaphase 1, anaphase
1, and telophase 1
• meiosis 2: prophase 2, metaphase 2, anaphase
2, and telophase 2
• In the first meiotic division, the number of cells is
doubled but the number of chromosomes is not.
40. • Synapsis (joining) of homologous chromosomes
produces tetrads (also called
_bivalents_____________).
• The two chromosomes may exchange fragments
between non-sister chromatids by a process
called __crossing over____________
51. Variation
• Sexual reproduction promotes variation because
each gamete (sperm or egg) contains a mixture of
genes from two different parents.
• Crossing-over and Independent assortment
promote variation.
• Variation is necessary for __natural
selection____________.
52. Significance of Meoisis
• Genetic Diversity through Crossing Over:
• Prophase I
• Genetic Diversity through Independent Assortment:
• During Metaphase I
56. Review
• Understand why cells duplicate
• What is interphase? Follow the phases of interphase
• Describe the major events of mitosis and cytokinesis
and understand what occurs at each stage-KNOW THE
ORDER
• Discuss how mitosis relates to cancer
• Understand Cloning
• Understand why we need meiosis
• Describe the major events that occur during the
separate divisions of meiosis-KNOW THE ORDER
• Describe how mitosis and meiosis differ
• Understand significance of synapsis and crossing over
• Be able to read a slide and identify the stage
• Describe Binary Fission
• Describe Aneuplody
Notes de l'éditeur
A mnemonic to help remember the stages of mitosis.
