The Cell Cycle PART 2 Honors Genetics Ms

The Cell Cycle PART 2 Honors Genetics Ms. Day

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

Phases of the Cell Cycle The cell cycle consists of l The mitotic (M) phase l Interphase (90% of the cell’s life) INTERPHASE G 1 C M yto ito kin si es s is ¡ M (M ITOT )P HA IC SE Figure 12. 5 S (DNA synthesis) G 2

Interphase can be divided into subphases l G 1 phase (GAP 1 phase) ¡ cell grows in size ¡varies most in length from cell to cell l S phase (synthesis phase) ¡DNA is copied (DNA replication) l Single Double ¡Other organelles are copied (ex: centrosomes in animal cells) l G 2 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 G 0 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 G 1, S, and G 2 of the cell cycle ¡ DNA is in chromatin form ¡ Nucleus & nucleolus present ¡ Longest phase of cell cycle

The Mitotic (M) phase l. 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 l Prophase l Metaphase l Anaphase l Telophase ¡ Cytokinesis

Mitotic Spindle Fibers l Two types of spindle fibers 1. Kinetochore fibers 2. Polar fibers

Prophase (X’s) “Pack Together” Chromatin Chromosomes l DNA “packs” together ¡ Mitotic spindle fibers form from centrosomes l Centrioles are in centromsomes in animals ¡ appear as asters in animals l 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 ¡

G 2 OF INTERPHASE PROMETAPHASE PROPHASE Aster Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Centromere Fragments of nuclear envelope Kinetochore Nonkinetochore microtubules Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule

Metaphase (X’s) “Meet in the Middle” ¡ ¡ Chromosomes line up in the middle of cell l 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

ure 12. 8 ¡ 1 In anaphase, sister chromatids separate l And move along the kinetochore microtubules toward opposite ends of the cell Kinetochore Spindle pole

NOT CHROMATIDS NOW!!!

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

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 l a cleavage furrow forms, which pinches the cell in two. In plant cells l 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.

ure 12. 9 A Cytokinesis: A Closer Look ¡ In Cleavage furrow Contractile ring of microfilaments 100 µm Daughter cells (a) Cleavage of an animal cell (SEM) animal cells l Cytokinesis occurs by a process known as cleavage, cleavage forming a cleavage furrow

¡ In plant cells, during cytokinesis l A cell plate forms Vesicles forming cell plate Wall of patent cell 1 µm Cell plate New cell wall Daughter cells Figure 12. 9 B (b) Cell plate formation in a plant cell (SEM)

G 2 OF INTERPHASE PROMETAPHASE PROPHASE Aster Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Centromere Fragments of nuclear envelope Kinetochore Nonkinetochore microtubules Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule

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

Mitosis in a plant cell Chromatine Nucleus Nucleolus condensing Chromosome Metaphase. The 2 Prometaphase. 3 1 Prophase. spindle is complete, 4 The chromatin We now see discrete and the chromosomes, is condensing. chromosomes; each attached to microtubules The nucleolus is consists of two at their kinetochores, beginning to identical sister are all at the metaphase disappear. chromatids. Later plate. Although not in prometaphase, the yet visible nuclear envelop will in the micrograph, fragment. the mitotic spindle is staring to from. Figure 12. 10 Anaphase. The 5 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.

Cell Cycle and Mitosis Animations ¡ http: //www. ucopenaccess. org/courses/APBiology. I/course %20 files/multimedia/lesson 17/lessonp. html ¡ http: //highered. mcgrawhill. com/olcweb/cgi/pluginpop. cgi? it=swf: : 535: : /sit es/dl/free/0072437316/120073/bio 14. swf: : Mitosis%20 a nd%20 Cytokinesis ¡ http: //www. sumanasinc. com/webcontent/animations/con tent/mitosis. html ¡ http: //www. johnkyrk. com/mitosis. html

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