The Cell Cycle Honors: Chapter 8.2-8.7

2 main parts to the cell cycle 1. Interphase 2. Cell Division (AKA--Mitotic Phase)

Parts of a Homologous Pair of Chromosomes Centromere Chromatid Homologous Chromosomes

Part 1. INTERPHASE G1 S G2 3 Stages:

C E L C Y C L E Interphase Period of cell growth and development that precedes mitosis and follows CYTOKINESIS (cell splitting) Longest phase of the cell cycle.

C E L C Y C L E Interphase G1 = Growth 1—most cell growth S = Synthesis—cell makes a copy of its DNA G2 = Growth 2—cell grows a little to prepare for division

2 main parts to the cell cycle 1. Interphase 2. Cell Division (AKA--Mitotic Phase)

Part 2. MITOSIS & Cytokinesis Cell Division P M A T 4 Stages:

**MITOS I S ** PROPHASE Chromatin condense & thicken – now called chromosome. The nuclear envelope breaks down Centrioles move to opposite "poles“ (or ends) of the cell

**MITOS I S ** METAPHASE The spindle (centriole) fully develops. The chromosomes align at the metaphase plate (middle)

**MITOS I S ** Paired chromosomes separate & begin moving to opposite ends (poles) of the cell. Spindle fibers lengthen & elongate the cell. Each pole contains a complete set of chromosomes. ANAPHASE

**MI TOS I S ** TELOPHASE Nucleus begins to form at opposite poles. The nuclear envelopes and nucleoli also reappear.

Last Event!!! CYTOKINESIS

C Y T O K I N E S I S CYTOKINESIS = the division of the original cell's cytoplasm. (There are now two separate cells)

-Write the Stage/Phase BIG!!! MITOSIS INDEX CARDS Blank Side: -Illustration -Description Lined Side: -Write the Stage/Phase BIG!!!

Mitosis At the end of Interphase Telophase Metaphase Anaphase Prophase

Plant Cell vs. Animal Cell C Y T O K I N E S I S CYTOKINESIS: Plant Cell vs. Animal Cell

MITOSIS CELL CYCLE Interphase Cell Division= Mitosis + Cytokinesis Prophase Metaphase Anaphase Telophase Interphase Cell Division= Mitosis + Cytokinesis

Do You Know the Stages of Mitosis? C E L C Y C L E Do You Know the Stages of Mitosis? CYTOKINESIS TELOPHASE ANAPHASE PROPHASE INTERPHASE METAPHASE ANAPHASE

Overview of the Cell Cycle

So why do our cells need to divide?? C Y C L E So why do our cells need to divide?? To heal any injuries For growth Replace lost or damaged cells

C E L C Y C L E Cell Cycle Regulation Cell growth and division are carefully controlled. Not all cells will go through the cell cycle at the same rate. Examples of cells NOT dividing often: Examples of cells rapidly dividing: Skin cells RBC Nerve cells Muscle cells Bone marrow Digestive tract cells

CANC E R What happens if cells LOSE the ability to CONTROL the cell cycle? http://www.yourcancertoday.com/ContentResources/Image/growth.jpg

CANC E R Cancer = uncontrolled cell growth . . . cancer cells do NOT respond to regulator signals . . . results in masses of cells called tumors . . . cancer = a disease of the cell cycle

What Causes Cancer? CANC E R Gene changes due to: diet tobacco use exposure to radiation exposure to chemicals Inherited genes (cyclins/growth factors don’t work) Immune System Failure Carcinogens

MEIOS I S Now we will look at how our sex cells are made. -Sperm & Egg What is the difference between a ‘sex cell’ and a ‘body cell?’

MEIOS I S Sex Cell Body Cell Sex cells have ½ the number of chromosomes of body cells “n” AKA: gamete AKA: haploid Body cells have twice the number of chromosomes as sex cells 2 “n” AKA: somatic AKA: diploid

MEIOSIS GAMETE FORMATION GAMETES= SEX CELLS Female Gamete= EGG Male Gamete= Sperm

MEIOS I S To create cells with ½ the genetic material you need to have a special process. This process, called MEIOSIS, occurs in the testes (men) and ovaries (females) in humans.

LET’s COMPARE!! M & M MEIOS I S

2 main parts to the cell cycle of SEX cells : 1. Interphase 2. Meiosis (AKA--Mitotic Phase)

Part 1. INTERPHASE G1 S G2 3 Stages:

WHAT HAPPENS DURING INTERPHASE???? C E L C Y C L E Interphase Interphase in all cells is the same. So, all you have to do is remember what you already know… WHAT HAPPENS DURING INTERPHASE????

C E L C Y C L E Interphase G1 = Growth 1—most cell growth HOMOLOGOUS PAIR- each chromosome that came from dad (orange) has a corresponding chromosome from mom (red) G1 = Growth 1—most cell growth S = Synthesis—cell makes a copy of its DNA G2 = Growth 2—cell grows a little to prepare for division At the end of interphase each chromosome consist of two identical sister chromatids attached at their centromeres.

2 main parts to the cell cycle of SEX cells : 1. Interphase 2. Meiosis (AKA--Mitotic Phase)

Part 2. MEIOSIS I & MEIOSIS II MEIOSIS

MEIOSIS I

**M E I O S I S ** MEIOSIS I The first part of Meiosis (called Meiosis I) is responsible for reducing the chromosome number by 1/2. This part consists of 4 phases: a. Prophase I (crossing over) b. Metaphase I (independent assortment) c. Anaphase I d. Telophase I & Cytokinesis

**M E I O S I S ** PROPHASE I Prophase I is the longest and most complex phase. All of the events that occurred during prophase of mitosis occur PLUS… Homologous chromosomes come together to form a TETRAD. CROSSING-OVER occurs.

** Exchanging of alleles** **M E I O S I S ** PROPHASE I CROSSING OVER: Portions of 1 chromatid breaks off and attaches to an adjacent chromatid on the homologous pair. ** Exchanging of alleles** TETRAD This INCREASES variability within a species!!!!

*MEI OS I S * LET’s COMPARE!! M & M

There are 2 major events: **M E I O S I S ** There are 2 major events: 1) Homologous chromosomes line up in the Middle of the cell… RANDOMLY= independent assortment (helps to mix up the genetic material) 2) Each centromere becomes attached to a spindle fiber. METAPHASE I

*MEI OS I S * LET’s COMPARE!! M & M

**M E I O S I S ** ANAPHASE I Homologous chromosomes separate and move towards the poles. The sister chromatids remain attached at their centromeres.

**M E I O S I S ** TELOPHASE I -Telophase I is the last step in meiosis I. (just like mitosis). -Following Telophase I.. Cytokinesis occurs and 2 haploid daughter cells are formed.

*MEI OS I S * LET’s COMPARE!! M & M

**M E I O S I S ** MEIOSIS I RECAP Q: What is the purpose of Meiosis I? A: To decrease the # of chromosomes by 1/2 Q: What 2 features of Meiosis I increase the diversity of the daughter cells? A: Crossing Over & Independent Assortment

MEIOSIS II

The steps of Meiosis II are IDENTICAL to Mitosis. ** MEIOSIS II Meiosis II comes directly after cytokinesis. No growth (interphase) takes place. Meiosis II is broken into 4 events: prophase II metaphase II anaphase II telophase II. The steps of Meiosis II are IDENTICAL to Mitosis.

**M E I O S I S ** MEIOSIS II

Meiosis I What happens here?? What happens here?? Interphase What happens here?? What happens here?? Prophase I Metaphase I What type of cell am I?? Anaphase I Telophase I Cytokinesis Images from: http://www.phschool.com/science/biology_place/biocoach/meiosis/teloi.html

Meiosis II Coming from Meiosis I Prophase II Metaphase II Telophase II Anaphase II Cytokinesis Images from: http://www.phschool.com/science/biology_place/biocoach/meiosis/teloi.html

MEIOSIS Coloring Activity ** MEIOSIS Coloring Activity Material: Coloring Activity Handout 4 colored pencils (different colors) Pen/Pencil Key: = Dad’s Chromosomes = Mom’s chromosomes = Nuclear Envelope = Centrioles & Spindles