Cell Cycle and Mitosis

1
Cell Cycle and Mitosis

• 12.1 Cell Cycle

2
What is the cell cycle?

• Repeating series of events
• Five stages
• Interphase (3 parts)
• G1
• S
• G2
• M phase (2 parts)
• Mitosis
• Cytokinesis

3
What happens in Interphase?

• G1
• Normal growth
• Recovery from last mitotic division
• S
• Replication of chromatids
• G2
• Synthesis of proteins for mitosis

4
Cell Cycle and Mitosis

• 12.2 M phase Mitosis and cytokinesis

5
What happens during the M phase?

• Mitosis
• Prokaryotes undergo binary fission instead
• Cytokinesis

6
What is a chromosome?

• Length of DNA with genes and noncoding regions
• Highly condensed version of chromatin
• Heterochromatin vs. euchromatin

7
What is mitosis?

• Division of nuclear material
• Duplicated chromosomes are split
• This creates unduplicated chromosomes
• Chromosome terminology
• Sister chromatids
• Kinetechore
• Centromere
• Diploid (2n) vs. haploid (1n)

8
What are the stages of mitosis?

• Prophase
• Prometphase
• Metaphase
• Anaphase
• Telophase

9
What happens in prophase?

• Nuclear envelope disappears
• Centrioles move apart
• Nucleous disappears
• Chromatin condenses to form chromosomes
• Recall that these are duplicated

10
What happens during prometaphase?

• Kinetechores appear
• Spindles attach
• Polar spindle fibers extend and overlap

11
What happens during metaphase?

• Duplicated chromosomes align along metaphase plate

12
What happens during anaphase?

• Sister chromatids pulled apart
• Chromosomes are now unduplicated

13
What happens during telophase?

• Reverse of prophase
• Cleavage furrow develops in animal cells

14
What is the second part of the M phase?

• Cytokinesis
• Cytoplasmic division
• Animal cells
• Contractile ring
• Plant cells
• Cell plate

15
Cell Cycle and Mitosis

• 12.3 Cell cycle control and cancer

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Why do cells undergo mitosis?

• Repair and replacement
• Apoptosis of somatic cells
• blebbing
• Stem cells
• Serve as reservoir for replacing old cells

17
What controls the cell cycle?

• Checkpoints
• G1
• Apoptosis if DNA is damaged
• G2
• M

18
What is cancer?

• Uncontrolled cell growth
• Characteristics
• Neoplasms (tumors)
• Benign vs. malignant
• Angiogenesis
• Metastasis
• Abnormal nuclei
• Undifferentiated (anaplasia)
• Lack contact inhibition
• No apoptosis

19
How does cancer occur?

• Mutations of cell repair genes
• Activation of telomerase
• Mutations of either/both
• Proto-oncogenes
• Become oncogenes
• Tumor suppressor cells

20
What are proto-oncogenes?

• gas pedal of cell division
• Mutated? oncogene
• Examples
• ras genes
• rasN (leukemia)
• BRCA1

21
What are tumor suppressor genes?

• Brake pedal of cell division
• If mutated ? loss of cell cycle control
• Examples
• p53 gene
• RB gene