Transcript Slide 1

CELL THEORY
1.Cells are the basic unit of life.
2.All living things are made up
of one or more cells.
3.All cells come from preexisting 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 or 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….
1. Reproduction
• In single-celled organisms, 2 separate individual
organisms are the result of the cell cycle.
2. Growth & development
• In multi-cellular organisms, rapid copying of cells
via the cell cycle add to the growing organism.
3. 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
1.Interphase (Cell is getting ready)
2.Mitosis (Cell Division-4 phases)
3.Cytokinesis (Chop/2 cells)
Interphase
1.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
1.Prophase
2.Metaphase
3.Anaphase
4.Telophase
Prophase (1st 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
• 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
The End of Mitosis
• 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