Cell prepares to reproduce Mitosis Cell prepares to reproduce

Cell Cycle

How do little elephants grow up to be BIG elephants?

Why do animals shed their skin?

What happens after a sperm fertilizes an egg?

In this time-lapse video of cell division in a newt lung cell, you can see a process that normally takes more than an hour occur in less than a minute.

Cell division Cell division is vital for all living organisms. This is the only process that can create new cells. Cell division always involves two main processes: the division of the nuclear contents the division of the cytoplasmic contents 2 Cytoplasms 2 Nuclei

Cell Division Cell Division — process by which a cell divides into 2 new cells Why do cells need to divide? Living things grow by producing more cells, NOT because each cell increases in size Repair of damaged tissues and cells If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell

Examples of tissue and cell repair

2 Daughter Cells Parent Cell The original cell is called the parent cell; 2 new cells are called daughter cells Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell Mitosis is part of the cell cycle 2 Daughter Cells Parent Cell

DNA Where is DNA located in the cell? DNA is located in the nucleus and controls all cell activities including cell division when the cell is about to divide they are coiled into a structure called a chromosome Long and thread-like DNA in a non-dividing cell is called chromatin

2 identical “sister” chromatids attached at an area in the middle called a centromere When cells divide, “sister” chromatids separate and 1 goes to each new cell

Coils up into chromosomes Chromatin to chromosomes illustration: Chromatin Coils up into chromosomes Duplicates itself Why does DNA need to change from chromatin to chromosome? More efficient division

News of the day! Newest commercially cloned puppy! http://www.sciencedaily.com/videos/9f87ae5572212a4e72cfa42e2c761682.htm

Chromosome number Every organism has its own specific number of chromosomes Examples: Human = 46 chromosomes or 23 pairs Dog = 78 chromosomes or 39 pairs Goldfish = 94 chromosomes or 47 pairs Lettuce = 18 chromosomes or 9 pairs

All somatic (body) cells in an organism have the same kind and number of chromosomes Examples: Human = 46 chromosomes Human skin cell = 46 chromosomes Human heart cell = 46 chromosomes Human muscle cell = 46 chromosomes Fruit fly = 8 chromosomes Fruit fly skin cell = 8 chromosomes Fruit fly heart cell = 8 chromosomes Fruit fly muscle cell = 8 chromosomes

Cell Cycle -- series of events cells go through as they grow and divide Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again

Interphase—period of cell growth and development DNA replication (copying) occurs during Interphase During Interphase the cell also grows, carries out normal cell activities, replicates all other organelles The cell spends most of its life cycle in Interphase Interphase is broken down in 3 phases G1 phase S phase (synthesis) G2 phase

Mitosis – division of the nucleus into 2 new ones, each with the same number of chromosomes Mitosis occurs in all the somatic (body) cells Why does mitosis occur? So each new daughter cell has nucleus with a complete set of chromosomes

Prophase Anaphase—(Apart) Anaphase—(Apart) Telophase—(Two) 4 phases of nuclear division (mitosis), directed by the cell’s DNA (PMAT) Prophase Metaphase—(Middle) Anaphase—(Apart) Anaphase—(Apart) Telophase—(Two)

Prophase Chromosomes coil up Nuclear envelope disappears Spindle fibers form

Metaphase—(Middle) Chromosomes line up in middle of cell Spindle fibers connect to chromosomes

Anaphase—(Apart) Chromosome copies divide Spindle fibers pull chromosomes to opposite poles

Telophase—(Two) Chromosomes uncoil Nuclear envelopes form 2 new nuclei are formed Spindle fibers disappear

In plant cells a cell plate forms Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides In animal cells the cytoplasm pinches in In plant cells a cell plate forms After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities

Summary: Cell Cycle http://www.cellsalive.com/mitosis_js.htm Interphase Mitosis (PMAT) Cytokinesis When cells become old or damaged, they die and are replaced with new cells

Prophase Anaphase Telophase Interphase Metaphase

Cell cycle Review Tasks SL: 14 - 17 Textbook pages: 20-29 http://tinyurl.com/cellcyclereview cell division and mitosis practice sheet Gizmo: complete gizmos on our class page, see me for username and password Kahoot:https://create.kahoot.it/?_ga=1.243390336.421732295.1455029933&devic eId=1ee26817-e71c-4c98-a062-3d2409b82620#quiz/72e531a5-ca9c-48d4-9f0c- 5a3d8ad3f985/done

Why are cells important?

Cell division is so essential to your life that it will take place in your body in your lifetime over 10 000 000 000 000 000 times!!!!! Like all split ups its not easy, it is going to maybe be a little messy, there is a lot of drama, and it does take a surprisingly long amount of time for cell division.

Quick Task There are some cells that speed through G1 (interphase) very quickly and don’t spend much time, if any, performing specialized functions before they divide again. Can you guess what type of cells these would be?

Quick Task What occurs if replication errors are left undetected and unfixed before mitosis?

Cell Division Control DNA controls all cell activities including cell division Some cells lose their ability to control their rate of cell division – the DNA of these cells has become damaged or changed (mutated) These super-dividing cells form masses called tumors

Cancer = uncontrolled cell division Cancer is not just one disease, but many diseases – over 100 different types of cancers

Chromosome Appearance & Location Phase Chromosome Appearance & Location Important Events Interphase Prophase Metaphase Anaphase Telophase Cytokinesis DNA replication, cell grows and replicates organelles DNA copies itself; chromatin Nuclear envelope disappears, spindle fibers form Chromosomes coil up Spindle fibers connect to chromosomes Chromosomes line up in the middle Spindle fibers pull chromosome copies apart to opposite poles Chromosome copies divide and move apart Nuclear envelopes reform, 2 new nuclei are formed, spindle fibers disappear Chromosomes uncoil back into chromatin Division of the rest of the cell: cytoplasm and organelles Chromatin

Cell cycle and cancer Review Tasks Things that you should have completed before the test! Workbook: pages 6-13, pages 14 - 19 (cell cycle and cancer) Textbook pages: read 20-37 cell division and mitosis flap book Additional resources: http://tinyurl.com/cellcyclereview Gizmo: complete gizmos on our class page, see me for username and password Work on your word definitions: interphase (G1,S,G2), DNA replication, mitosis, prophase, metaphase, anaphase, telophase, cytokinesis, parent cell, daughter cells, DNA, nuclear envelope, spindle fibres, centrioles, chromatin, sister chromatids, chromosomes, tumour, mutation, cancer