PART 2 Honors Genetics Ms. Day The Cell Cycle PART 2 Honors Genetics Ms. Day

The Cell Cycle The mitotic phase alternates with interphase in the cell cycle Interphasemitosisinterphasemitosis

Phases of the Cell Cycle The cell cycle consists of The mitotic (M) phase Interphase (90% of the cell’s life) INTERPHASE G1 S (DNA synthesis) G2 Cytokinesis Mitosis MITOTIC (M) PHASE Figure 12.5

Interphase can be divided into subphases G1 phase (GAP 1 phase) cell grows in size varies most in length from cell to cell S phase (synthesis phase) DNA is copied (DNA replication) Single  Double Other organelles are copied (ex: centrosomes in animal cells) G2 phase (GAP 2 phase) More growth and preparation (make proteins) for mitosis http://www.cellsalive.com/cell_cycle.htm

Another G phase of Interphase Called G0 phase called the resting phase The cell exits the “cycle” and (usually) does NOT reproduce again Ex: muscle cells, nerve cells, red blood cells

Interphase “Intermission” or “Inbetween” not part of mitosis Includes stages G1, S, and G2 of the cell cycle DNA is in chromatin form Nucleus & nucleolus present Longest phase of cell cycle

The Mitotic (M) phase Is made up of 2 parts 1. Mitosis division of the nucleus (called Karyokinesis) 2. Cytokinesis  division of the cytoplasm

Mitosis Continuous pathway (Early, Mid, & Late) Consists of 4 phases and cytokinesis Prophase Metaphase Anaphase Telophase Cytokinesis

Mitotic Spindle Fibers Two types of spindle fibers Kinetochore fibers Polar fibers

Prophase (X’s) “Pack Together” Chromatin  Chromosomes DNA “packs” together Mitotic spindle fibers form from centrosomes Centrioles are in centromsomes in animals appear as asters in animals Microtubule Organizing Centers (MTOC’s) (in plants) Centrosomes & Spindle fibers move towards “poles” Late: Nucleus and nucleolus disappear kinetochore fibers attach to each kinetochore on each chromosome  they begin to migrate toward the cell center

Kinetochore microtubule G2 OF INTERPHASE PROPHASE PROMETAPHASE Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Aster Centromere Fragments of nuclear envelope Kinetochore Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule Figure 12.6 Nonkinetochore microtubules

Metaphase (X’s) “Meet in the Middle” Chromosomes line up in the middle of cell Called equatorial or metaphase plate Kinetochore spinder fibers pull and tug chromosomes to line up

Anaphase (V’s) “Adios and Away” SISTER CHROMATIDS separate and begin moving to opposite ends (poles) of the cell Polar fibers lengthen and elongate the cell Late anaphase  each pole contains a complete set of single chromosomes NOTE: This is the only time there is DOUBLE the amount of DNA in ONE cell

In anaphase, sister chromatids separate And move along the kinetochore microtubules toward opposite ends of the cell 1 Spindle pole Kinetochore Figure 12.8

NOT CHROMATIDS NOW!!!

TELOPHASE AND CYTOKINESIS Centrosome at one spindle pole Daughter chromosomes METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Spindle Metaphase plate Nucleolus forming Cleavage furrow Nuclear envelope forming Figure 12.6

Telophase (V’s) “Two New Cells” The spindle fibers dissappear Two daughter nuclei reform at the two poles Two daughter nucleoli reform at the two poles Nuclear envelopes reforms from the fragments of the parent cell’s nuclear envelope Chromosomes  chromatin

Cytokinesis “Division of the Cytoplasm” Occurs in Late telophase In animal cells a cleavage furrow forms, which pinches the cell in two. In plant cells vesicles from the Golgi apparatus produce a cell plate at the middle of the cell At the end of cytokinesis, there are two distinct IDENTICAL daughter cells.

Cytokinesis: A Closer Look Cleavage furrow Contractile ring of microfilaments Daughter cells 100 µm (a) Cleavage of an animal cell (SEM) Figure 12.9 A In animal cells Cytokinesis occurs by a process known as cleavage, forming a cleavage furrow

(b) Cell plate formation in a plant cell (SEM) In plant cells, during cytokinesis A cell plate forms Daughter cells 1 µm Vesicles forming cell plate Wall of patent cell Cell plate New cell wall (b) Cell plate formation in a plant cell (SEM) Figure 12.9 B

Kinetochore microtubule G2 OF INTERPHASE PROPHASE PROMETAPHASE Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Aster Centromere Fragments of nuclear envelope Kinetochore Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule Figure 12.6 Nonkinetochore microtubules

TELOPHASE AND CYTOKINESIS Centrosome at one spindle pole Daughter chromosomes METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Spindle Metaphase plate Nucleolus forming Cleavage furrow Nuclear envelope forming Figure 12.6

Mitosis in a plant cell Nucleus Chromatine condensing Chromosome 1 Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is staring to from. Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelop will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of cell as their kinetochore microtubles shorten. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divided the cytoplasm in two, is growing toward the perimeter of the parent cell. 2 3 4 5 Nucleus Nucleolus Chromosome Chromatine condensing Figure 12.10

Cell Cycle and Mitosis Animations http://www.ucopenaccess.org/courses/APBiologyI/course%20files/multimedia/lesson17/lessonp.html http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120073/bio14.swf::Mitosis%20and%20Cytokinesis http://www.sumanasinc.com/webcontent/animations/content/mitosis.html http://www.johnkyrk.com/mitosis.html

Remember… “IPMATc” Let’s do the Mitosis Hand Cheer!