Cell Cycle and Mitosis

9.1 Cell Cycle

What is the cell cycle? Repeating series of events Five stages Interphase (3 parts)

G1

S G2

M phase (2 parts) Mitosis Cytokinesis

What happens in Interphase? G1

Normal growth Recovery from last

mitotic division S

Replication of chromatids

G2

Synthesis of proteins for mitosis

Cell Cycle and Mitosis

9.2 M phase: Mitosis and cytokinesis

What happens during the M phase? Mitosis

Prokaryotes undergo binary fission instead

Cytokinesis

What is a chromosome? Length of DNA with

genes and noncoding regions

Highly condensed version of chromatin Heterochromatin vs.

euchromatin

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)

What are the stages of mitosis? Prophase Prometphase Metaphase Anaphase Telophase

What happens in prophase? Nuclear envelope

disappears Centrioles move apart Nucleous disappears Chromatin condenses to

form chromosomes Recall that these are

duplicated

What happens during prometaphase? Kinetechores appear Spindles attach Polar spindle fibers extend and overlap

What happens during metaphase? Duplicated chromosomes align along

metaphase plate

What happens during anaphase? Sister chromatids pulled apart Chromosomes are now

unduplicated

What happens during telophase? Reverse of prophase Cleavage furrow develops in animal

cells

What is the second part of the M phase? Cytokinesis

Cytoplasmic division Animal cells

Contractile ring Plant cells

Cell plate

Cell Cycle and Mitosis

9.3 Cell cycle control and cancer

Why do cells undergo mitosis? Repair and replacement

Apoptosis of somatic cells blebbing

Stem cells Serve as reservoir for replacing old cells

What controls the cell cycle? Checkpoints

G1

Apoptosis if DNA is damaged

G2

M

What is cancer? Uncontrolled cell growth Characteristics

Neoplasms (tumors) Benign vs. malignant Angiogenesis Metastasis Abnormal nuclei Undifferentiated (anaplasia) Lack contact inhibition No apoptosis

How does cancer occur? Mutations of cell

repair genes Activation of

telomerase Mutations of

either/both Proto-oncogenes

Become oncogenes Tumor suppressor

cells

What are proto-oncogenes? “gas pedal” of cell

division Mutated oncogene Examples

ras genes rasN (leukemia) BRCA1

What are tumor suppressor genes? Brake pedal of cell

division If mutated loss of

cell cycle control Examples

p53 gene RB gene