Title: Mitosis and the Cell Cycle Date ______
1Mitosis and the Cell Cycle Date ______
2Introduction to Cell Division
- Life is handed down from one generation of
organisms to the next in the form of cells. - A unicellular organism reproduces by dividing in
two - Multi-cellular organisms begin life as a single
cell a zygote - Repeated cell division produces the many cells of
the body.
3Introduction to Cell Division
- When a cell divides, it must pass on the genetic
information needed for the new cells to function - The DNA that is found in the chromosomes of the
nucleus carries the genetic information. - Mitosis is the process that produces two new
nuclei with the same number and kinds of
chromosomes as the original nucleus - Mitosis ensures that each new cell inherits a
complete set of the parent cells genetic
information.
4Introduction to Cell Division
- Examples of uses of mitosis
-
- Unicellular organism ? 2 organisms
- Fertilised egg cell ? multi-cellular organism
- Old cells ? new cells
- Repair of damaged tissue
5Introduction to Cell Division
- Each kind of cell has a typical life-span which
begins when the cell is formed by division of the
parent cell and ends when the cell itself divides
or dies. - Yeast cell 2 hours
- Amoeba a few days
- Human embryo cell 15-20 minutes
- Human adult cell 8 hours to 100 days
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7Overview The Key Roles of Cell Division
- The continuity of life is based upon the
reproduction of cells, or cell division - Unicellular organisms reproduce by cell division
- Multicellular organisms depend on cell division
for - Development from a fertilized cell
- Growth
- Repair
20 µm
200 µm
(b) Growth and development. This micrograph
shows a sand dollar embryo shortly
after the fertilized egg divided, forming
two cells (LM).
(c) Tissue renewal. These dividing bone
marrow cells (arrow) will give rise to new
blood cells (LM).
8Cell Division Key Roles
- Genome cells genetic information
- Somatic (body cells) cells
- Gametes (reproductive cells) sperm and egg cells
- Chromosomes DNA molecules
- Diploid (2n) 2 sets of chromosomes
- Haploid (1n) 1 set of chromosomes
- Chromatin DNA-protein complex
9Cell Division Key Roles Cont
Chromatids replicated strands of a
chromosome Centromere narrowing waist of
sister chromatids Kinetochore The chromosomal
attachment point for the spindle fibers located
within the centromeres. Mitosis nuclear
division Cytokinesis cytoplasm
division Meiosis gamete cell division
10Packaging DNA
Structure of a chromosome interaction.
11The Cell Cycle
- Interphase (90 of cycle) G1 phase growth
S phase synthesis of DNA G2 phase
preparation for cell division - Go phase Quiescence temporary/reversible
state of rest - Cellular senescence is the phenomenon where cells
lose the ability to divide.
Mitotic phase Mitosis nuclear division
Cytokinesis cytoplasm division
12Mitosis
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
13Prophase
- Chromosomes visible
- Nucleoli disappear
- Sister chromatids
- Mitotic spindle forms
- Centrosomes move
14Late Prophase
- Nuclear membrane fragments
- Spindle interaction with chromosomes
- Kinetochore develops
15Metaphase
- Centrosomes at opposite poles
- Centromeres are aligned
- Kinetochores of sister chromatids attached to
microtubules (spindle)
16Anaphase
- Paired centromeres separate sister chromatids
liberated - Chromosomes move to opposite poles
- Each pole now has a complete set of chromosomes
17Telophase
- Daughter nuclei form
- Nuclear envelopes arise
- Chromatin becomes less coiled
- Two new nuclei complete mitosis
18Mitosis in a Animal cells
19Mitosis in a Animal Cells continued
20Mitosis in a Plant Cells
21Cytokinesis
- Cytoplasmic division
- Animals cleavage furrow
- Plants cell plate
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23Prokaryotes (bacteria)
- Reproduce by a type of cell division called
binary fission - The bacterial chromosome replicates
- The two daughter chromosomes actively move apart
Origin of replication
Cell wall
Plasma Membrane
E. coli cell
Bacterial Chromosome
Two copies of origin
Origin
Origin
24The sequential events of the cell cycleare
directed by a distinct cell cycle control system,
which is similar to a clock
25The clock has specific checkpointswhere the cell
cycle stops until a go-ahead signal is received
26Cell Cycle regulation
- Growth factors
- Density-dependent inhibition
- Anchorage dependence
27Cancer
- Transformation
- Tumor benign or malignant
- Metastasis