unit #6 - the cell cycle the white sections summarize key information and vocabulary terms are...

Unit #6 - The Cell Cycle

• The white sections summarize key information and vocabulary terms are underlined.

Dreams

I look to the sky and what do I see?A castle, a rainbow, and dreams for me,An end to this battle that I must fight,To rid my feelings of depression and fright,An end to cancer is not far away,It will be here someday... someday.

~ Anonymous

http://www.youtube.com/watch?v=IeUANxFVXKc

Observations

Introduction Textbook Reference pg. 204-206

• Much as your body goes through different stages in your life, the cells and viruses do too.

• The life cycle of the cell is known as the cell cycle.

• In this unit we will discuss the processes of the cell cycle (the making of new cells).

http://www.wadsworth.org/BMS/SCBlinks/mcewen/Media/fig_1_cell_mitosis.jpg



5 Reasons Cells DivideTextbook Reference pg. 203

1. Growth- an organism will increase in size as the number of cells making up that organism increase

2. Differentiation- cells develop specialized cells to carry out specific tasks

ex: the heart cell versus the muscle cell3. Repair- to repair lost or damaged cells

ex: mending of skin, blood vessels and bone

4. Regeneration- ability to replace a lost limb or body part by rapid cell division ex: starfish, lizard

5 Reasons Cont.

• And finally…5. Reproduction – the making of a new organism

http://ghr.nlm.nih.gov/handbook/illustrations/mitosismeiosis;jsessionid=B368026AB01E981849F2E31603F7154F



Cell Division• The splitting of a single cell into two new daughter cells

is called cell division. • This will occur when a cell reaches it’s maximum size

and the nucleus initiates cell division; proteins called cyclins and enzymes begin this process.

http://protist.i.hosei.ac.jp/PDB/Images/

Sarcodina/Heliozoa/

Actinosphaerium/cell_division_1.jp

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Two Types of Cell Division Textbook Reference pg. 204-206

• Mitosis- the division of body cells (somatic) due to the splitting of the nucleus to create two new cells.

• Meiosis – the creation of gametes (sex cells) by cutting the # of chromosomes in half to create sex cells. http://ghr.nlm.nih.gov/handbook/illustrations/mitos

ismeiosis;jsessionid=B368026AB01E981849F2E31603F7154F




Chromosomes Textbook Reference pg. 203-204

• In order for a cell to survive, the genetic information is needed.

• Cells tightly coil their DNA into chromosomes during the process of mitosis.

• Review: We have already learned that genetic information is held within the nucleus (of Eukaryotes) in the form of DNA.

• Therefore, it is very important that cells must copy their genetic information before dividing.

http://www.koshland-science-museum.org/exhibitdna/images/dna/intro02.gif

Chromosomes Cont.

http://www.learner.org/channel/courses/biology/images/archive/fullsize/1940_fs.jpg

Chromosomes Cont.

• During mitosis, identical chromosomes pair up and are now called sister chromatids (1), held together by a centromere (2).

• Sketch it!

http://upload.wikimedia.org/wikipedia/en/5/54/Chromosome.png

Stage #1 Interphase

Textbook Reference pg. 204-205

1. Interphase = The period of growth for the cell before cell division (the longest stage) which is broken up into the following phases:

• G1 – growth and development

• S – copies of the DNA

• G2 – the cells organelles and centrioles (in animals only) copied

http://dedunn.edublogs.org/files/2011/06/mitosis-26hzktr.jpg



Knowledge Check

During the course of the life of a cell, there is a

complicated series of checkpoints to

ensure that everything is

going according to plan.

Stage #2 Prophase

Textbook Reference pg. 206-208

2. Prophase = The DNA condenses and forms chromosomes.

• Identical chromosomes (Xsomes) join

• Nucleus disappears

• Centrioles (the organelles which form the spindles) move to opposite poles

• Spindle fibers (long strings that help the cell divide) begin to grow

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Stage #3 Metaphase

Textbook Reference pg. 208

3. Metaphase = Xsomes pairs line up along the middle of the cell on the the metaphase plate

• Centrioles have moved to the poles; spindle fibers are still attached to chromosomes.




Metaphase Cont.

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNArep/images/metaphase1_pc.jpg



Stage #4 Anaphase

Textbook Reference pg. 208

4. Anaphase = The centromeres divide and spindle fibers pull the chromosomes apart from their partners

• The chromatids move to opposite poles of the cell



Stage #5 Telophase Textbook Reference pg. 209

5. Telophase = The nuclei reform at each end of the cell

• Chromosomes uncoil into chromatin (or loose genetic material)

• Spindles release Xsomes and shorten.

• The cell begins to pinch as the cytoplasm begins to divide




Stage # 6 Cytokinesis Textbook Reference pg. 209

6. Cytokinesis = In animals, the cell membrane is drawn inward (cleavage furrow).

• In plants, a cell plate is built to create new cells walls and membranes.

• Each half has one nucleus and gets own set of centrioles (and other organelles)

• The cell is pinched in half until membrane meets.

• The cell is now two and enters Interphase (G1).

• Animation

http://alevelnotes.com/content_images/

i77_dwa_1_mitosis.gif

• “During mitosis, after all the genetic material is sorted out, the cell splits all of its cytoplasmic goodies in two and sends them to opposite ends. It then constricts in the middle and eventually ‘pinches’ in half, producing two daughter cells. The location at which the pinching in occurs is known as the cleavage furrow.” Image

Cytokinesis Cont.

Visualizing Mitosis

http://wiki.district87.org/images/9/9f/Plant_cells.jpg

Prophase

Interphase Metaphase

Anaphase

Telophase

Ex Mnemonics• Ms. Flores’s Example:

I = “I’ll

P = probably

M = make

A = apple

T = tarts for

C = Christmas!”

• Student Created Example:

I = “Intelligent

P = people

M = make

A = all

T = the

C = cash!”

• The word “mnemonic” means “memory tool”. It is a phrase or saying to remember a list.

• Student Created Example:

I = “Irritating

P = pupils

M = make

A = all

T = teachers

C = cringe!”

• The mnemonic goes on the outside of the flap and the actual stage goes on the inside of the flap.

In Conclusion

• At the beginning of the unit, we discussed how cancer relates to mitosis.

• Cancer is thought to be caused by a change in the controlling genes that regulate the cell cycle.

• Mitosis is the division of somatic body cells to create identical daughter cells.

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