Transcript Mitosis PowerPoint

MITOSIS
Reproduction by Asexual Means
Regents Biology
OBJECTIVES
Upon completion of this unit students will be able to:
1. Name and describe the two types of reproduction and the two basic processes
involved in cell division.
2. Explain what happens in interphase and in the stages of mitosis.
3. Differentiate interphase and mitosis in plant and animal cells.
4. Discuss how mitosis is controlled.
5. Discuss what cancer is.
6. Describe the types of asexual reproduction and vegetative propagation.
KEY WORDS
anaphase
asexual reproduction
binary fission
budding
cell plate
centromere
chromatid
chromatin
chromosomes
cytokiniesis
interphase
metaphase
mitosis
prophase
regeneration
sexual reproduction
spindle fiber
sporulation
telophase
vegetative propagation
OVERVIEW
Cell division is the simplest form of reproduction. This process
involves several complex steps that result in the division of one
cell into two identical cells. Single-celled organisms are able
to produce more individuals like themselves using the process of
cell division. Some multi-celled organisms may also utilize this
process to reproduce identical offspring or result in the
overall growth of the organism. “Asexual” (literally, “without
sex”) is the term used to describe this mode of reproduction.
Asexual reproduction involves the production of new
organisms of a species from a cell or cells of a single
parent organism. There is no fusion of cells or cell nuclei in
asexual reproduction. Instead, there is a duplication of the
nucleus in the production of more cells with characteristics
identical to those of the single parent organism.
TYPES OF REPRODUCTION
• There are two basic types of reproduction:
1.ASEXUAL: THERE IS ONLY ONE PARENT;
NO SPECIAL REPRODUCTIVE
CELLS/ORGANS ARE INVOLVED; THE NEW
INDIV. IS SEPARATE FROM THE PARENT
2. SEXUAL: INVOLVES THE UNION OF TWO
NUCLEI FROM SPECIAL CELLS; THESE ARE
USUALLY PRODUCED BY TWO SEPARATE
ORGANISMS
• Some organisms produce only asexually,
others produce only sexually, and still others can
reproduce by either method.
MITOSIS AND CYTOKINESIS
•In our cytology unit we learned that the cell theory
states that ALL CELLS ARISE FROM PRE-EXISTING
CELLS BY CELL DIVISION. This type of cell division
is called MITOTIC CELL DIVISION and involves two
distinct stages:
1.MITOSIS: NUCLEAR DIVISION; A
DUPLICATION OF THE CONTENTS OF THE
PARENT CELL NUCLEUS, FOLLOWED BY
AN ORDERLY SEPARATION OF THOSE
CONTENTS INTO TWO NEW, IDENTICAL
NUCLEI
2. CYTOKINESIS (CYTOPLASMIC DIVISION):
THE CYTOPLASM OF THE CELL IS DIVIDED
INTO TWO PARTS, EACH CONTAINING ONE
OF THE NEWLY FORMED NUCLEI; THE
DAUGHTER CELLS SHARE THE SAME # OF
CHROMOSOMES AS WELL AS IDENTICAL
GENETIC CHARACTERISTICS
A. Nuclear Material
• The hereditary material of the nucleus is DNA
(DEOXYRIBONUCLEIC ACID)
• The information necessary for the
SYNTHESIS of all components of each cell is
stored in THE STRUCTURE OF DNA.
• The DNA also includes information that
DETERMINES THE MAKEUP AND FUNCTION
OF THE ORGANISM and this information must
be passed on to all cells produced.
• DNA is found in CHROMATIN (LONG, THIN,
TWISTING THREADS)
• During cell division, THE CHROMATIN
BECOMES ORGANIZED INTO
CHROMOSOMES
• Each type of organism has a specific number of
CHROMOSOMES in its body cells; HUMANS
HAVE 46 CHROMOSOMES
• When cells reproduce, the new cells must
have the SAME number of chromosomes as
the original cell.
• The number of chromosomes in the body cells
of an organism is CONSTANT; since each
chromosome makes up only part of the DNA,
each cell must receive an entire set of
chromosomes to function properly.
B. Interphase
• Interphase is NOT a phase of mitosis; the phases of mitosis are
PROPHASE, METAPHASE, ANAPHASE AND TELOPHASE
• When a cell is between mitotic cycles, it is in INTERPHASE
and is also known as THE RESTING STAGE
• Interphase lasts from THE END OF ONE CELL DIVISION TO
THE BEGINNING OF THE NEXT
Interphase in a plant cell
• During interphase, EACH CHROMOSOME
MAKES A COPY FOR ITSELF (REPLICATES)
AND IS ACTUALLY A DOUBLE
CHROMOSOME
• DNA appears AS A TANGLED,
THREADLIKE MASS OF CHROMATIN
• Near the nucleus are the CENTRIOLES,
which also REPLICATE DURING
INTERPHASE FORMING 2 PAIRS
C. The Phases of Mitosis
1. Prophase
• During prophase, THE DOUBLE CHROMOSOME
BECOMES VISIBLE
• The two halves of each double chromosome are
called CHROMATIDS and are connected at the
CENTROMERE
•In early prophase, THE TWO PAIRS OF CENTRIOLES MOVE
TOWARDS THE POLES
•Fibers extending outward from the centrioles are called ASTERS
•PLANT CELLS DO NOT have CENTRIOLES and therefore there
is no formation of ASTERS.
•Other threadlike fibers extend between the poles: SPINDLE
FIBER
•In late prophase, the double
chromosomes move toward the
EQUATOR and THE NUCLEAR
MEMBRANE AND NUCLEOLUS
DISAPPEAR
Prophase in a
plant cell
2. Metaphase
MY FAVORITE PHASE!!!!! 
•During metaphase, THE CENTROMERES ARE
LINED UP ON THE EQUATOR
•In late metaphase, EACH DOUBLESTRANDED CHROMOSOME GIVES RISE TO
TWO SINGLE-STRANDED, IDENTICAL
CHROMOSOMES
Metaphase in a
plant cell
3. Anaphase
• During anaphase, THE DUPLICATE
CHROMOSOMES MOVE APART TO
OPPOSITE POLES WITH THE AID OF THE
SPINDLE FIBERS
Anaphase in a
plant cell
4. Telophase
• Telophase begins when THE CHROMOSOMES REACH THE
POLES
• The chromosomes elongate, uncoil, and begin to appear like
chromatin (as in pre-interphase)
• The spindle and asters disappear
• A nuclear membrane forms around each daughter nucleus
• The nucleoli reappear
• The nuclear division of an animal cell is complete!
Telophase in an
animal cell
D. Cytokinesis
• Cytokinesis is NOT a phase of mitosis, it is THE
DIVISION OF THE CYTOPLASM AFTER MITOSIS
• Cytokinesis begins during late ANAPHASE and is
completed during TELOPHASE
• In ANIMAL CELLS, cytokinesis is accomplished by
the “PINCHING” or furrowing of the cell membrane.
• This “pinching in” results in THE FORMATION OF
TWO DAUGHTER CELLS OF THE SAME SIZE
• In PLANT CELLS, the rigid cell wall does not pinch
during telophase. Instead, A CELL PLATE FORMS
ACROSS THE MIDDLE OF THE CELL
CENTRIOLES
CHROMATIN
ASTERS
NUCLEAR
MEMBRANE
SPINDLE
FIBERS
CENTROMERE
NUCLEOLUS
CHROMATIDS
SPINDLE
FIBERS
POLE
EQUATOR
POLE
CLEAVAGE FURROW
DAUGHTER CELLS
SISTER
CHROMATIDS
E. CONTROL OF MITOTIC CELL DIVISION
• Exactly how mitosis is started and controlled
is unknown to us.
• In unicellular organisms, it is thought that AN
INCREASE IN SIZE TRIGGERS MITOSIS
• Normally, in multicellular organisms, CELL
DIVISION OCCURS ONLY AS NEEDED FOR
REPAIR AND GROWTH
• CANCER: UNCONTROLLED CELL
DIVISION
Normal mitotic cell division results in the production of new
cells for growth and for the repair of damaged or worn-out
body tissues. It is a process that is controlled within the
cell itself, and that occurs countless times in living things
without flaw. However, in some cells at some times, the
mitotic process appears to break down and begins to occur
so rapidly that insufficient time is available for normal
replication and chromosome separation. This rapid,
abnormal cell division is known as cancer.
Cancer of the larynx
In a very short time cancer may produce
a large number of such abnormal cells,
which begin to crowd out the normal
tissues, resulting in damage to these
tissues and often in the death
of the host organism.
F. TYPES OF ASEXUAL REPRODUCTION
• Because asexual reproduction involves only
MITOTIC CELL DIVISION, each offspring has
the same hereditary information as its parent.
• Asexual reproduction results in STABLE
CHARACTERISTICS WITHIN A SPECIES
FROM ONE GENERATION TO THE NEXT
• Asexual reproduction is generally EFFICIENT
in that it is generally RAPID and often results in
the production of LARGE MEMBERS OF
OFFSPRING.
1. BINARY FISSION
· Binary fission is THE SIMPLEST FORM OF ASEXUAL
REPRODUCTION
· The parent organism DIVIDES INTO TWO EQUAL PARTS
· Each of the daughter cells BECOMES A SEPARATE INDIVIDUAL
AND GROWS TO NORMAL SIZE
· No parent is left by this method because THE PARENT HAS
BECOME TWO INDIVIDUALS
· Organisms that perform binary fission: BACTERIA, PROTOZOA,
AMEOBA
BINARY FISSION is
accomplished when a
single cell undergoes
mitosis followed by equal
cytoplasmic division,
forming two daughter cells
having roughly the same
size and shape and
containing identical genetic
information.
2.BUDDING
· Budding is where THE PARENT ORGANISM DIVIDES INTO TWO
UNEQUAL PARTS
· Budding results in DAUGHTER CELLS OF UNEQUAL SIZE, BUT
CONTAINING IDENTICAL GENETIC INFORMATION
· The larger of the two cells may divide rapidly several more times,
producing A CHAIN OR COLONY OF DAUGHTER CELLS
· Organisms that perform budding: YEAST, HYDRA
BUDDING is when new embryonic
cells begin to form by mitosis
within the mature tissues of the
organism. As these embryonic
tissues begin to differentiate
(specialize) they take on the
physical appearance of the parent
organism. After a period of
growth, the new organism, or
“bud”, identical to the parent
organism, separates from the
parent and begins to live an
independent existence.
3. SPORULATION/SPORE FORMATION
• Sporulation is the FORMATION OF SPECIALIZED
REPRODUCTIVE CELLS CALLED SPORES
• Spores can be formed SEXUALLY OR ASEXUALLY and
contain A NUCLEUS SURROUNDED BY CYTOPLASM
• Asexually formed spores are the products of MITOTIC CELL
DIVISION, and are a common method of reproduction in FUNGI
(MOLD, MUSHROOM), ALGAE, PROTOZOA
SPORULATION is the formation of
specialized reproductive cells, known as
spores, within the parent organism. Each
spore contains a nucleus surrounded by
cytoplasm. When these spores are
released from the parent plant and land
in an environment containing conditions
favorable to their growth, they begin to
undergo mitotic cell division. The spores
of most species require moisture and
warmth to germinate. The mitotic
divisions result in the formation of a new
multicellular organism genetically
identical to the original parent organism.
4. REGENERATION
• REGENERATION: THE ABILITY OF AN ORGANISM
TO REGROW LOST BODY PARTS
• Organisms that reproduce by regeneration include:
HYDRA, PLANARIA, STARFISH, EARTHWORM
• The capacity for organisms to regenerate decreases as
THEY BECOME MORE COMPLEX (I.E.,
INVERTEBRATES REPRODUCE AND REPAIR
DAMAGED TISSUES BY REGENERATION MORE
READILY THAN VERTEBRATES)
• Although simple organisms have great capacities for
regeneration, THEY DO NOT REPRODUCE BY THIS
METHOD UNDER NATURAL CIRCUMSTANCES
5. VEGETATIVE REPRODUCTION
• Vegetative structures: ROOTS, STEMS, LEAVES
and function in NUTRITION AND GROWTH OF
PLANTS
• When vegetative structures give rise to a new
plant, the process is called VEGETATIVE
PROPAGATION
• In vegetative reproduction, undifferentiated
(unspecialized) cells divide mitotically and then
become specialized to GIVE RISE TO AN
INDEPENDENT PLANT
• The new plant has THE SAME HEREDITARY
CHARACTERISTICS AS ITS PARENT
• Vegetative propagation may occur NATURALLY
OR ARTIFICIALLY
1.NATURAL VEGETATIVE PROPAGATION
• BULBS: BULBS BUD FROM PARENT BULBS AND IS MADE
UP OF EMBRYONIC TISSUES THAT FORM LEAVES AND
FLOWERS; UNDERGROUND STEM W/ LEAF STRUCTURE;
ONION AND TULIP
• TUBERS: UNDERGROUND STEMS FOR STORING EXCESS
FOOD; POTATO
• RUNNERS: STEMLIKE STRUCTURES THAT GROW FROM
THE MAIN STEM OF THE PARENT PLANT OVER THE
SURFACE OF THE SOIL; POISON IVY AND STRAWBERRIES
2.ARTIFICIAL VEGETATIVE PROPAGATION
• CUTTINGS: REMOVING A PORTION OF THE
ROOT, STEM, OR LEAF AND STIMULATING IT TO
GROW AND REPLACE THE MISSING PARTS OF
ITS BODY AND BECOME AN INDEPENDENT
ORGANISM; COLEUS AND GERANIUM PLANTS
• GRAFTINGS: EMBRYONIC TISSUES (CAMBIUM)
OF ROOT STOCK ARE ATTACHED TO LIKE
TISSUES OF AN UPPER STEM TAKEN FROM THE
PARENT PLANT TO BE REPRODUCED;
COMMERCIAL GROWERS PRODUCE LARGE
QUANTITIES OF GENETICALLY IDENTICAL
PLANTS FOR SALE; ORANGES AND EMPIRE
APPLES
ADVANTAGES:
a) Vegetative propagation ensures THE
PRODUCTION OF NEW PLANTS EXACTLY
LIKE THE PARENT
b) The development of a plant by vegetative
propagation often TAKES LESS TIME THAN
DEVELOPMENT FROM SEED
c) Plants bearing SEEDLESS FRUIT can only
be grown by vegetative propagation
d) GRAFTING can be used to obtain higher
yields of fruits or nuts.