CELL THEORY
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Cells are the basic unit of life.
All living things are made up of one or more cells.
All cells come from pre-existing cells.
Asexual Reproduction
Asexual Reproduction: Produces offspring identical to the parent.
EX. Budding: a type of asexual reproduction in which a cell or group of cells pinch off from the
parent to form a new individual.
EX. Mitosis (Oh My toes): want the same kind of cells on your toes.
Mitosis is a type of asexual reproduction when a nucleus undergoes cell division in
which two daughter cells are formed, each containing a complete set of chromosomes.
Cell Division
Two Types
Meiosis (Sexual Reproduction)
Sex Cells (Sperm & Egg)
Mitosis (Asexual Reproduction)
2 Daughter cells (similar cells)
Cell Cycle/Cell Division
Cell Cycle is the pattern of division & growth of a cell.
It involves the copy & distribution of the genome (genetic information/DNA).
The cell cycle serves 3 main functions….
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Reproduction
In single-celled organisms, 2 separate individual organisms are the result of the cell cycle.
Growth & development
In multi-cellular organisms, rapid copying of cells via the cell cycle add to the growing
organism.
Tissue & renewal
In multi-cellular organisms that have reached maximum growth, the cell cycle renews &
replaces older cells to maintain and organism’s size & function.
Cell Division/Cell Cycle
Mitosis:
Mitosis (Oh My toes): want the same kind of cells on your toes.
Mitosis is a type of asexual reproduction when a nucleus undergoes cell division in
which two daughter cells are formed, each containing a complete set of chromosomes.
Continue Cell Cycle
Somatic cells are all the body’s cells except the reproductive cells; egg & sperm.
Somatic cells contain 46 chromosomes.
Chromosomes are condensed chromatin into double rods (chromatids) of genetic
material.
Chromatin
The mass of very long, thin fibers of DNA & proteins that are
found unwound within the nucleus.
Chromatid
½ of the double-rodded structure of a chromosome
3 Stages of Cell Division/Cell Cycle
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Interphase
Mitosis
Cytokinesis
Interphase
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Stage 1: Interphase (21 hours)
Interphase is the longest of the 3 stages of the Cell Cycle
The cell begins to grow & enlarge
Replication of DNA
The primary process that takes place during Interphase is the replication
of DNA.
DNA (deoxyribonucleic acid) is the sequence of nitrogen base pairs
that determines the structure of proteins and serves as the genetic
code of life.
Replication is the process by which the DNA makes an exact
copy of itself.
The cell produces structures that will be used to help the cell divide into 2
new cells.
Centromere connects the chromatids or double rods of
chromosomes.
Centrioles are organelles used to separate & pull chromosomes
into new nuclei.
Spindle fibers are bands that extend from the centriole &
attach to the chromosome & pull it into separate nuclei.
Interphase
Stage 2: Mitosis
Mitosis
4 Phases
Mitosis is the 2nd stage of the Cell Cycle and takes <50 minutes.
During Mitosis, 2 nuclei are created and 1 copy of the DNA created during
Interphase is distributed to each of the nuclei.
(Falwell) My toes…You want the same cells for skin cells, toe nails, hair etc.
Remember: Skin cells, hair cells, etc, are Somatic Cells
4 Phases of Mitosis
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Prophase
Metaphase
Anaphase
Telophase
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Prophase (1 phase of Mitosis)
Prophase is the longest phase of Mitosis.
Chromatin in the nucleus condenses to form chromosomes.
Spindle fibers form a bridge between the ends of the cell.
Nuclear envelope breaks down
Prophase
Prometaphase
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Recently a new phase; Prometaphase, has been added in between Prophase and
Metaphase.
Centrioles move to opposite sides of the nucleus.
Kinetochore is a specialized structure located at the
centromere region forms.
Metaphase
Chromosomes line up across the metaphase plate, an imaginary plane located
across the center of the cell.
Each chromosome attaches to a spindle fiber at its centromere
Metaphase
Anaphase
The centromere split.
The 2 chromatids separate.
1 chromatid is drawn by its spindle fiber to 1 end of the cell.
The other chromatid moves to the opposite end.
Cell stretches out as the opposite ends are pushed apart.
Anaphase
Telophase
Chromosomes begin to stretch out & lose their rod like appearance.
A new nuclear envelope forms around each region of chromosomes.
Telophase
Remember 3 stages of cell division/cell cycle
Stage 1: Interphase
Stage 2: Mitosis
Phase 1: Prophase
Phase 2: Metaphase
Phase 3: Anaphase
Phase 4: Telophase
Stage 3: Cytokinesis
Stage 3: Cytokinesis
Cytokinesis (< 15 minutes)
The cytoplasm divides.
The 1st sign of cleavage is the appearance of a cleavage furrow.
A cleavage furrow is shallow groove in the cell surface near the old
metaphase plate.
Cytokinesis actually begins during Telophase, the last phase of Mitosis.
2 new cell membranes form around the 2 new cells.
The new cells have an identical set of chromosomes and half of the
organelles
Cytokinesis