Mitosis Chapter 12

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MitosisChapter 12

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Mitosis

• Cell division
• Produce 2 daughter cells
• Same genetic information
• Genome

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Mitosis

• Asexual reproduction
• Growth
• Repair

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Prokaryotes

• Nucleoid
• Circular DNA
• No nucleus

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Eukaryotes

• Chromosomes
• DNA
• Chromatin
• Complex of DNA proteins
• Makes up chromosomes
• Humans 46 chromosomes
• Dogs 78 chromosomes

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Karyotype

• Display of the chromosomes

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Karyotype
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Turners syndrome
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Eukaryotes

• Haploid(n)
• Single set of chromosomes (23 in humans)
• Diploid(2n)
• Twice the haploid number or two sets (46)
• Homologous chromosomes
• 2 chromosomes that match up
• One from the mother one from the father
• Homologs
• One of the pair of chromosomes

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Eukaryotes

• Chromatid
• Duplicated chromosome
• Centromere
• Attachment to another chromatid
• Prior to cell division each chromosome replicates
  

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Fig. 12-5
INTERPHASE
S (DNA synthesis)
G1
Cytokinesis
G2
Mitosis
MITOTIC (M) PHASE
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Cell cycle

• Cell cycle
• Events that occur to produce two cells
• 1. Interphase (G1, S, G2)
• 2. Mitosis
• 3. Cytokinesis

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Cell cycle

• Most of cycle is spent in interphase
• Rate of division depends on job of the cell.
• Liver cells may divide rapidly
• Mature muscle cells do not divide at all
• Few cells will be in mitosis at a time
• Most are in interphase

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Cell cycle

• G1 or Gap 1 phase the cell is preparing for the S
  phase.
• Chromosomes are single
• Can last weeks to years or happen very quickly

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Cell cycle

• S phase DNA replication happens
• 2 sister chromatids
• G2 or Gap 2 phase cell prepares for division
• Mitochondria other organelles replicate
• Microtubules begin to form
• Chromosomes condense

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Cell cycle

• Mitosis
• Nucleus its contents divide
• Distributed equally
• Forming two daughter cells
• Cytokinesis
• Cytoplasm divides in two.

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Interphase

• Growth phase of the cell
• G1, S, G2

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Interphase
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Prophase

• Beginning of mitosis
• Chromosomes continues to condense
• Mitotic spindle forms
• Begins to move chromosomes to center
• Nuclear membrane disintegrates
• Nucleolus disappears

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Prophase
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Metaphase

• Chromosomes line up in center of cell
• Centromeres become aligned along the cells center

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Metaphase
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Anaphase

• Microtubules shorten
• Separates the sister chromatids
• Chromosomes move towards the poles

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Anaphase
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Telophase

• Chromosomes are at the poles
• Nuclear envelope reforms
• Nucleolus reappears
• Chromosomes uncoil or de-condense

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Telophase
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Cytokinesis

• Cytoplasm separates
• Animal cells
• cleavage furrow pinches the cells in two
• Plant cells
• cell plate is formed between the cells
• Grows until a new cell wall is formed

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Cytokinesis
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Fig. 12-9
Vesicles forming cell plate
Wall of parent cell
1 µm
100 µm
Cleavage furrow
Cell plate
New cell wall
Daughter cells
Contractile ring of microfilaments
Daughter cells
(a) Cleavage of an animal cell (SEM)
(b) Cell plate formation in a plant cell (TEM)
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Binary fission

• Prokaryotes produce 2 daughter cells by binary
  fission

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Binary fission

• 1. Replication of the DNA
• Origin of replication
• Specific location on the DNA
• 2. Two DNA molecules move to the ends of the cell
• 3. Septation
• Formation of a new cell membrane a septum.

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Binary fission

• 4. Septum begins to grow inward
• 5. Cell pinches into two cells.

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Cell cycle
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Cell cycle control system

• Consists of special proteins
• Protein kinases cyclins
• Regulate if cell stops or proceeds in the cycle
• Receives information from the environment
• Other cells determine if the cell should divide
  or not

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Cell cycle control system

• Check points
• G1, G2 and M
• Signals
• Growth factors
• Density-dependent inhibition
• Anchorage dependence

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Fig. 12-14
G1 checkpoint
Control system
S
G1
G2
M
M checkpoint
G2 checkpoint
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p53

• Protein that works at a checkpoint at G1 in the
  cell cycle
• p53 determines if the DNA is damaged
• If so it stimulates enzymes to fix it
• Cell division continues
• Unable to repair damage
• Cell suicide occurs

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p53

• Helps keep damaged cells from dividing
• Cancer cells p53 is absent or damaged
• p53 protein is found on the p53 gene
• Considered a tumor-suppressor gene
• Cigarette smoking causes mutations in this gene

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Tumor

• Abnormal growth of cells
• Due to a malfunction in the control system
• Abnormal cells grow uncontrollably
• Benign
• Non-cancerous growth

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Tumor

• Malignant
• Cancerous growth
• Metastasis
• Spread of cancer to distant locations

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Henrietta Lacks

• 1951 developed cervical cancer
• Before cancer treatment
• Cells were removed
• First cells to grow in vitro
• Outside of the body
• Cell line is now known as the HeLa cell line
• Helped in biomedical research