Ch 3 Cell Cycle 1 Fig 3 21

Ch 3 Cell Cycle 1

Fig. 3. 21 2

Cell Cycle Major phases: 1. Interphase 2. Mitosis (PMAT) 3. Cytokinesis Mitotic Phase (2&3) 3

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Checkpoints • Special proteins are involved at certain times to control the cell cycle • Restriction Point occurs at end of G 1& allows it to continue to Mitosis (PMAT) and divide • If no division- stops and does its job G 0 5

Cell Cycle 2 phases: Interphase & mitotic phase all subphases cell grows Produces proteins and all organelles BOTH mitosis and cytokinesis 24 hrs 10 - 12 hours 5 - 6 hours 4 - 6 hours 1 hour

Frequency of Division Divide a lot: skin cheek (epithelia) lining of stomach and small intestine Don’t Divide : nerve 7

Telomeres 8

Stages of Cell Cycle • (Interphase) MITOSIS • Prophase • Metaphase • Anaphase • Telophase & Cytokinesis • (I Probably Mixed All This up)

Interphase • • • 90% of Cell Cycle Divided into 3 phases: G 1, S, & G 2 Nucleolus visible Chromosomes replicating Nuclear membrane intact Single Centrosome replicates in animal cells • Organelles are replicating

Prophase • Chromatin shortens and condenses • Chromosomes appear as sister chromatids (X) • Nucleolus disappears • Nuclear membrane disappears • Centrosomes (Centrioles) move to the poles • Spindle fibers form

Chromosome is composed of 2 chromatids Centromere holds chromatids together

Prometaphase • Spindle fibers attach to Kinetochores during prometaphase • Kinetochore microtubules

Metaphase • Chromosomes meet @ equator/middle • Centrioles are @ poles • Longest phase (20 minutes)

Anaphase • Spindle fibers shorten and pull chromosome by centromere • Chromosomes move apart/away • Sister chromatids separate • Shortest phase • Cohesins cleaved by enzymes 2 sets of chromosomes!!

Telophase & Cytokinesis • Chromosomes are @ poles • Chromosomes lengthen & Nuclear envelope reforms • Nucleoli reappear • Cleavage furrow / Cell plate forms

Cytokinesis • Animal Cell Cleavage Furrow • Plant Cell Plate

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Comparing Mitosis & Meiosis • Mitosis • Genetically identical • Genetic Variation • Reduction Division 2 n 2 n n n n

Cell differentiation 20

Progenitor cell 21

Fig. 3. 23 22

Apoptosis 23

apoptosis 24