Agenda for 12/1- Cell Cycle, Division (Mitosis) Bellwork New Information: Cell Cycle, Mitosis Lab/Activity: Identifying Stages of the Cell Cycle- virtual lab Link to quizlet: Honors- http://quizlet.com/join/dKABWXfWn CP- http://quizlet.com/join/TNxRntCAm

Bellwork Domestic horses have 64 chromosomes. How many chromosomes should be in an egg cell of a female horse? A. 16 B. 32 C. 64 D. 128

Cell Cycle and Cell Division (Mitosis) What is mitosis? Why is it important?

Cell Division 3 reasons for mitotic cell division (mitosis): Growth Repair Replacement Parent cell divides into two identical daughter cells

Cell Division Cells divide to make new cells- DNA is replicated so each daughter cell gets an exact copy. DNA condenses into chromosomes during mitosis. 5

Cell Division Humans have 46 chromosomes, 23 from each parent. Haploid cells: only one of each chromosome (n) Diploid cells: two of each chromosome (2n)

Cell Cycle (click for video clip) G1 phase M phase S phase G2 phase

Interphase- longest G1 Phase Cell growth S Phase DNA replication preparation for mitosis M Phase mitosis and cytokinesis Allium G1 M phase S G2

Interphase Nucleus and nuclear envelope are visible. One or more nucleoli are visible. The rest of the nucleus is filled with chromatin.

Figure 10-5 Prophase Interphase Cytokinesis Metaphase Telophase Anaphase

Prophase pro- = first; first stage of mitosis Nuclear envelope breaks down Chromatin condenses into chromosomes Centrioles move to opposite poles of the cell Spindle fibers attach to chromosomes at the centromere. (plant cells have microtubule organizing centers instead of centrioles)

Metaphase Chromosome line up in the Middle of the cell Chromosome centromeres attach to the spindle at the poles of the cell

Anaphase Chromosome centromeres separate and sister chromatids move Apart to the opposite ends of the cell

Telophase Chromosomes precipitate back into strands of DNA (chromatin) A new nuclear membrane begins to form around each of the two new clumps of DNA

Cytokinesis Same time as Telophase Animal Cells: (“cell splitting”) Same time as Telophase Animal Cells: cytoplasm splits as the cell membrane draws inward (cleavage furrow) and splits the cell in two Plant Cells: cytoplasm splits as a cell plate forms between the two new nuclei, then a new cell membrane

Cell Cycle and Mitosis I P M A T C I Protect Mothers And Their Children Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

Cell Cycle and Mitosis Virtual Lab Go to http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/36m.html Make a table like the one you’ll see before the activity begins. Answer the following questions: Which phase of the cell cycle is longest? How do you know? Which is shortest, and how do you know?

Lab Objectives To list the phases of the cell cycle in the order in which they occur. To list the phases of the M-phase of the cell cycle (Mitosis) and explain what happens during each. To illustrate/draw what happens during each phase of Mitosis. To identify the role of cell structures during cell division (centrioles, chromatin, chromosomes, nucleus). To learn the importance of cell division for organisms (asexual reproduction, growth, repair).

Mitosis in Allium Root Interphase Prophase Metaphase

Mitosis in Allium Root Anaphase Telophase

Bellwork What are the 4 phases of the cell cycle? What are the 4 phases of mitosis? What is the significance of the phrase “I Protect Mothers And Their Children?” What phases are shown below?

Binary Fission Prokaryotes (bacteria) reproduce by a type of cell division called binary fission. In binary fission the bacterial chromosome replicates and the two daughter chromosomes actively move apart.

G1 phase M phase S phase G2 phase

The Cell Cycle Control System The events of the cell cycle are directed by a cell cycle control system, similar to a clock. Figure 12.14 Control system G2 checkpoint M checkpoint G1 checkpoint G1 S G2 M

The Cell Cycle Control System There are specific checkpoints where the cell cycle stops until a go-ahead signal is received. G1 checkpoint G1 G0 (a) If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle. (b) If a cell does not receive a go-ahead signal at the G1checkpoint, the cell exits the cell cycle and goes into G0, a non-dividing state. Figure 12.15 A, B

Control of Cell Division In density-dependent inhibition crowded cells stop dividing. Most animal cells exhibit anchorage dependence in which they must be attached to a substratum to divide. Cells anchor to dish surface and divide (anchorage dependence). When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition). Normal mammalian cells. The availability of nutrients, growth factors, and a substratum for attachment limits cell density to a single layer. (a) 25 µm Figure 12.18 A

Control of Cell Division Cancer cells: no density-dependent inhibition or anchorage dependence. Do not respond normally to the body’s control mechanisms and form tumors. Loss of the cell cycle controls. 25 µm Cancer cells do not exhibit anchorage dependence or density-dependent inhibition. Cancer cells. Cancer cells usually continue to divide well beyond a single layer, forming a clump of overlapping cells. (b) Figure 12.18 B

Control of Cell Division Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body where they may form secondary tumors.

Eukaryotic Cell Division Mitosis- normal cell division Parent cell divides into two identical daughter cells (diploid = 2n) n = number of types of chromosomes Meiosis- cell division resulting in sex cells (gametes) Parent cell divides into 4 daughter cells, each with half the number of chromosomes (haploid = 1n)

Mitosis 2 diploid daughter cells formed, just like parent cell (two of each chromosome) Preceded by interphase (G1, S, G2 phase) Mitosis: Prophase Metaphase Anaphase Telophase

Figure 10-5 Prophase Interphase Cytokinesis Metaphase Telophase Anaphase

Meiosis occurs in somatic cells to produce sex cells 4 haploid daughter cells formed (only one of each chromosome) Preceded by interphase and DNA replication Meiosis I Meiosis II

Meiosis Meiosis I- like mitosis but only one copy of each homologous chromosome goes to each new cell; two new cells formed Prophase I Metaphase I- homologous chromosomes line up on equator Anaphase I- homologous chromosomes separate Telophase I- two new cells, each with half the genetic material (one copy of each chromosome) Meiosis II- the two cells formed in Meiosis I divide again Basically like Mitosis

Mitosis vs. Meiosis Animation Mitosis- 2 diploid cells produced Meiosis- 4 haploid cells produced Why? Mitosis- 2 exact copies of parent cell- to replace cells Meiosis- 4 haploid cells, only half the genetic material, so gametes can combine to produce a new organism