Download Cell Division or Cell Reproduction

4/18/2017
Cell
Reproduction
Mitosis and Meiosis
Cell Division or Cell
Reproduction
Two types of cell division:
– Mitosis - most common type of cell division
– Meiosis – process that produces sex cells for reproduction of
organisms.
– Mitotic Index –the ratio between the number of cells in a population undergoing mitosis to the
number of cells in a population not undergoing mitosis. (the ratio of cells dividing to cells
resting)
– Chromosome - the part of a cell that contains the genes which control how an animal or plant
grows and what it becomes
– Diploid - containing two complete sets of chromosomes, one from each parent
– Haploid - having a single set of unpaired chromosomes
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Mitosis
Remember by: Mitosis has a T like ‘two’ or ‘twins’ because
it results in two twin cells replacing the original cell
– Cell division process that occurs in most cells in the body
– Results in two diploid daughter cells that are identical to and replace the original cell
– Each daughter cell has the same number of chromosomes as the original cell
– Chromosomes in the daughter cells are exact replicas of the chromosomes in the original
(parent) cell.
– Functions:
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Growth of organism from single celled fertilized egg to adult*
Replacement/regeneration of damaged or ‘old’ cells*
Asexual reproduction
* These are the main functions of mitosis, occurring in all organisms.
Meiosis
– Occurs only in reproductive organs
– Cell division process that results in sex cells, ovum (egg) and sperm
– Results in four haploid cells with half the number of chromosomes as the original cell
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In males, these become 4 sperm cells
In females, only one of these becomes a viable ovum (egg cell) and three polar bodies that disintegrate.
– Chromosomes in the haploid cells are unique compared to each other and the original cell due to
crossing over
– Crossing over - process in genetics by which the two chromosomes of a homologous pair
exchange equal segments with each other.
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Latin and Greek prefixes
Prefixes:
– A – not, without
– Ana – up, back, again
– Inter – within, inside
– Intra – between,
– Meta – between, along, after
– Mito -- thread
– Pro – forward, favoring, before
– Sis – condition, state
Phase – a characteristic
form, appearance, or
stage of development
that occurs in a cycle
– Telo – end
Stages of Cell Division:
Interphase
Mitosis
Meiosis
– Near the end of this phase,
the cell copies its DNA in
preparation for cell division
– Near the end of this phase,
the cell copies its DNA in
preparation for cell division
– Resting phase – time
between phases of cell
division
– Resting phase – time
between phases of cell
division
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Stages of Cell Division:
Interphase
Stages of Cell Division:
Prophase/Prophase 1 - First phase of cell division
Mitosis
– Chromosomes become
visible as paired chromatids
– Spindle fibers begin to form
– Nuclear membrane
disintegrates
Meiosis
– Chromosomes become
visible as paired chromatids
and attach to nuclear
membrane
– Paired chromosomes
exchange gene sequences
– Spindle fibers begin to form
– Nuclear membrane
disintegrates
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Stages of Cell Division:
Prophase/Prophase 1
Mitosis - Prophase
Meiosis – Prophase 1
Stages of Cell Division:
Prometaphase/Prometaphase 1
Mitosis
Meiosis
– Spindle fibers attach to each
of the chromosomes
– Spindle fibers from opposite
sides attach to one of each
pair of chromosomes
– Centrioles at opposite ends
of the cell
– Centrioles at opposite ends
of the cell
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Stages of Cell Division:
Metaphase/Metaphase 1
Mitosis
Meiosis
– Spindle fibers begin to tug
each chromosome toward
opposite ends of the cell
– Spindle fibers begin to tug
chromosomes toward
opposite ends of the cell
– Chromosomes line up along
the metaphase plate, an
imaginary line in the middle
of the cell
– Chromosomes line up along
the metaphase plate, with
pairs on opposite sides of the
line
Stages of Cell Division:
Metaphase/Metaphase 1
Mitosis - Metaphase
Meiosis – Metaphase 1
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Stages of Cell Division:
Anaphase/Anaphase 1
Mitosis
Meiosis
– The fibers pull the sister
chromatids to opposite ends
of the cell
– Sister chromatids do not
separate
– Chromosomes break at
centromeres and
– Chromosomes pairs
separate, one moving to each
end of the cell
Stages of Cell Division:
Anaphase/Anaphase 1
Mitosis - Anaphase
Meiosis – Anaphase 1
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Stages of Cell Division:
Telophase/Telophase 1 and Cytokinesis
Mitosis
Meiosis
– Mitosis is now considered
complete
– For sperm cells, cell division is
approximately equal, for egg
cells, forms one large and one
small cell.
– Cytokinesis – division of the
cytoplasm and formation of cell
wall/membrane occurs.
– Chromatids – now considered
chromosomes – arrive at
opposite ends of the cell,
– new nuclear membrane forms
– Cytokinesis – division of the
cytoplasm and formation of cell
wall/membrane occurs.
– Chromosomes pairs arrive at
opposite ends of the cell
– New nuclear membrane may
form
Stages of Cell Division:
Telophase/Telophase 1
Mitosis - Telophase
Meiosis – Telophase 1
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Stages of Cell Division:
Cytokinesis
Mitosis - Cytokinesis
Meiosis – Cytokinesis
Stages of Cell Division:
Interphase II (Meiosis)
Mitosis
– Mitosis and cytokinesis are
complete
Meiosis
– Chromosomes do not
replicate
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Stages of Cell Division:
Prophase II
Meiosis
– Spindle fibers begin to form
– Nuclear membrane
disintegrates
– Chromosomes do not attach
to the nuclear membrane or
exchange gene sequences.
Stages of Cell Division:
Metaphase II
Meiosis
– Chromosomes line up along
the metaphase plate
– Spindle fibers begin to tug
each chromosome toward
opposite ends of the cell (as
in mitosis metaphase)
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Stages of Cell Division:
Anaphase II
Meiosis
– (as in mitosis) The fibers pull
the chromatids apart
– Chromatids move to opposite
ends of the cells
Meiosis
Stages of Cell Division:
Telophase II
– Chromatids arrive at either end
of the dividing cell and a new
nuclear membrane forms
– For males, there are two
dividing cells
– For females, there is one
dividing cell; as in Telophase 1,
most of the cytoplasm will be
concentrated in one of the two
forming cells
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Stages of Cell Division:
Cytokinesis
Meiosis
– The cell(s) complete division
– For males, there are now
four haploid cells
– For females, there is one
haploid cell and two polar
bodies (failed cells – one
from each of Meiosis 1 and
Meiosis 2)
CELL DIVISION IS NOW
COMPLETE.
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