THE CELL CYCLE and CELL DIVISION

Think about it… why do cells stay small? DNA Overload = Limit to Cell Growth The information stored in that DNA is able to meet all of the cell’s needs in a small cell If a cell grows too large, the DNA cannot produce enough proteins to supply the cell

CELL DIVISION -before it becomes too large, a growing ‘parent’ cell divides into 2 ‘daughter’ cells **Before cell division occurs, the cell replicates all of its DNA, one set/daughter **2 main stages of eukaryotic cell division: Mitosis – division of the cell nucleus Cytokinesis – division of cell cytoplasm

Liver cell completes cell division – Magnification 11,500x

Chromosomes Genetic information is passed from one generation to the next on chromosomes (made of DNA). Chromosomes are only visible in most cells during cell division (other times, the DNA is in the not visible chromatin state) Before cell division, the DNA condenses into compact structures, chromosomes

Chromosomes Once copied, each chromosome consists of two identical “sister” chromatids. Centromere –attachment After cell division, each new cell receives one sister chromatid Sister chromatids Centromere

THE CELL CYCLE

The Cell Cycle During the cell cycle: a cell grows prepares for division divides Interphase is the period of growth that occurs between cell divisions -followed by mitosis and cytokinesis

The Cell Cycle

synthesizes proteins & organelles increases in size synthesizes proteins & organelles chromosome replicated DNA synthesis takes place Enters S phase completes cycle organelles and molecules required for cell division are produced Once G2 is complete, the cell is ready to start the M phase—Mitosis

Mitosis The process of cell division which results in the production of two daughter cells from a single parent cell The daughter cells are identical to one another and to the original parent cell.

Animated Cycle http://www.cellsalive.com/cell_cycle.htm http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html

Mitosis Prophase Metaphase Anaphase Telophase

Chromosomes (paired chromatids) Mitosis: PROPHASE Spindle forming Prophase Chromosomes (paired chromatids) Centromere Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.

Prophase 1st & longest phase Spindle forming Prophase 1st & longest phase Centrioles separate and take up positions @ nuclear poles Spindle, a microtubule structure, forms between the centrioles Nuclear envelope breaks down. Centromere Chromosomes (paired chromatids)

Mitosis: METAPHASE Centriole Spindle Centriole Metaphase

Metaphase The chromosomes line up across the center of the cell aka Centriole Metaphase The chromosomes line up across the center of the cell aka metaphase plate Microtubules connect the centromeres to the fibers of the spindle. Spindle

Individual chromosomes Mitosis: ANAPHASE Individual chromosomes Anaphase

Anaphase Sister chromatids separate into individual chromosomes. The chromosomes move and separate into two groups. Individual chromosomes

Nuclear envelope reforming Mitosis: TELOPHASE Nuclear envelope reforming Telophase

Telophase Chromosomes gather at opposite ends of the cell & lose their distinct shape New nuclear envelopes forms around each cluster Spindle breaks apart & nucleoli reappear

CYTOKINESIS Cytokinesis

Cytokinesis Not a phase of mitosis Cell membrane pinches in and the cytoplasm is split between the 2 cells Each daughter cell has an identical set of duplicate chromosomes

Cytokinesis in Plants Cell plate forms midway between the divided nuclei. Cell plate Cell wall

Animal Mitosis Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Plant Mitosis Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Cells in Mitosis http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html http://web.mac.com/mrgaskell/iWeb/Science%20Extras/Mitosis%20Slides.html Things to look: Shape of Cell & If there is a division forming between cells Chromosomes & Location Presence of a nucleus

Mitosis Animations http://www.johnkyrk.com/mitosis.html http://www.youtube.com/watch?v=VlN7K1-9QB0 http://outreach.mcb.harvard.edu/animations/biochem.swf http://www.hybridmedicalanimation.com/anim_mitosis.html http://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html

Controls on Cell Division Normal cells reproduce until they come into contact with other cells. When cells come into contact with other cells, they respond by not growing. This shows that cell growth and division can be turned on and off.

Cell Cycle Regulators Regulated by a specific protein called cyclin Cyclin concentration rises and falls in time with the cell cycle Internal Regulators: -Proteins responding to events inside cell - Allow the cell cycle to proceed only when certain processes have happened inside the cell. External Regulators: -Proteins responding to events outside cell -direct cells to speed up/slow down the cell cycle

Cancer: Uncontrolled Cell Growth cells lose the ability to control growth. Cancer cells do not respond to the signals that regulate the growth of most cells. Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues. Metastasis-cancer cells may break loose from tumors and spread throughout the body

Cancer Cells http://science.education.nih.gov/supplements/nih1/cancer/activities/activity2_animations.htm

Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Prophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Meiosis cell division by which germ cells (eggs and sperm) are produced. One parent cell produces four daughter cells (not genetically identical)

During meiosis, DNA replicates once, but the nucleus divides twice. Daughter cells have half the number of chromosomes (n=haploid) found in the original parent cell (2n=diploid)

Meiosis I Prophase 1: Each chromosome duplicates and remains closely associated. These are called sister chromatids. Metaphase 1: Chromosomes align at the center of the cell. Anaphase 1: Chromosome pairs separate with sister chromatids remaining together. Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the chromosome pair.

Prophase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Prophase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Metaphase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Telophase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

4 haploid daughter cells are formed MEIOSIS II Prophase 2: DNA does not replicate. Metaphase 2: Chromosomes line up at the center of the cell Anaphase 2: Centromeres divide and sister chromatids move separately to each pole Telophase 2: Cell division is complete 4 haploid daughter cells are formed

Prophase II http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Metaphase II http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Telophase II http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Meiosis http://www.biosci.uga.edu/almanac/bio_103/notes/apr_3.html.

Meiosis Animation http://www.rothamsted.bbsrc.ac.uk/notebook/courses/guide/movie/meiosis.htm

Crossing Over A section of 1 chromosome switches places with the same section from the other chromosome http://www.accessexcellence.org

http://post.queensu.ca/

Differences in Mitosis & Meiosis Asexual Cell divides once Two daughter cells Genetic information is identical Meiosis Sexual Cell divides twice Four haploid daughter cells Genetic information is different

Purpose of Reproduction To make sure a species can continue. Definition: Reproduction is the process by which an organism produces others of its same kind.

Asexual Reproduction A new organism produced from 1 organism The offspring will have hereditary material uniform with the hereditary material of the parent organism. This means they will be genetically alike.

Sexual Reproduction Requires two sex cells – egg and sperm The egg and sperm join to form an entirely new organism Different from the parent organism

IMPORTANT! Asexual reproduction results in offspring that are genetically identical to the parent organism Sexual reproduction results in offspring that are genetically different from the parent organisms-more energy so…. WHY IS IT WORTH IT?

Comparison Animations http://www.pbs.org/wgbh/nova/baby/divi_flash.html http://www.usoe.k12.ut.us/curr/science/sciber00/7th/genetics/sciber/animatin.htm