January 5, 2011 Quiz on the Cell – Make sure to read Chapter 8 Define Vocabulary 8.1 PS Lab 8.1 Notes Mitosis Note cards… Mitosis Sequencing ?? Of the Day List the limitations to cell size: Explain why??

Biology 1/6/11 Stamp on Vocab 8.1 PS Lab 8.1 Notes – fill in sheet Mitosis Index Card Follow Rubric ?? Of the Day: What phase of the cell cycle is the longest? WHY?

Size Limitations of the Cell A Cell is forced to Divide for the following reasons. 1. The cell gets too big. Small cells have a larger surface area compared to the volume. This means a comparatively larger area to move things in (like food) and out (like wastes) of the cell. 2. Diffusion moves materials too slowly across (relatively) large spaces. 3. The cell’s DNA can’t keep up with the production of proteins necessary for survival.

Cell Division also occurs: 1. For GROWTH of a multicellular organism 2. To REPAIR old, worn out CELLS (surface layers) 3. To replace lost or DYING cells. 4. A form of ASEXUAL reproduction for SINGLE-CELLED organisms

Cell Reproduction Cell Division is the process by which NEW cells are produced from OLD ones. Mitosis is the division of the NUCLEAR MATERIAL or DNA. This is important because each cell needs an exact COPY. The end result of mitosis is the production of NEW cells that are IDENTICAL to the parent cell and is then followed by the division of the CYTOPLASM called cytokinesis.

Some cells, like SKIN cells, divide throughout the lifetime of the organism, other cells may or may not DIVIDE after maturity. (Ex: SKIN cells only divide when repair of the organ itself is required and MUCSCLE and NERVE cells lose their ability to divide.

CHROMOSOMES Chromosomes consist of DNA and are the carriers of our GENETIC information that must be passed from generation to generation. There are 46 pieces of DNA in the human cell ( the number of chromosomes determines an organism’s classification – i.e. the fruit fly has 4 chromosomes).

Biology 1/7/11 Grab a paper off of the stool Get a box of color pencils Finish up Notes on Mitosis Mitosis Index Cards

The pieces of DNA spends most of the time in the nucleus, in strands called CHROMATIN The Chromatin can be seen in the nucleus when the STRAND coils tightly and forms rod-shaped structures (CHROMOSOMES) during the latter part of the cell cycle (mitosis). (Page 212) CHROMATIN

Cell Cycle The cell cycle is the sequence of GROWTH and DIVISION of a cell. In cells that continuously divide; it is an ongoing, repetitive cycle of events that includes growth, REPLICATION of nuclear material, mitosis, and CYTOKINESIS.

Parts of the Cell Cycle Interphase – BUSIEST period of the cell. This is when the cell carries out the copying of cell. Consist of 3 phases:  G1= Rapid growth and metabolic activity (production of PROTEINS)  S = DNA synthesis (replication)  G2 = Growth and REPLICATION (centrioles replicate)

B. Mitosis in Animal Cells – period of cell division. Consists of 4 phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

1. Prophase Chromatin coils up into visible CHROMOSOMES and each one consists of 2 CHROMATID joined by a centromere (see pg. 212). Nucleolus begins to disappear and NUCLEAR ENVELOPE begins to break down. Centrioles begin to move to POLES (ends) of the cell The SPINDLES (microtubule structure) forms between the centrioles (see pg.214) Spindle Fibers Nuclear Envelope CentromereCentriole Chromosomes

2. Metaphase Chromosomes are moved to the equator (CENTER) of the cell with spindle fibers attached to each side of the CHROMOSOME. When this phase begins, each chromosome consists of two SISTER CHROMATIDS joined by a centromere. X Sister Chromatid Equator Spindle Fibers Centromere

3. Anaphase The CHROMOSOMES are pulled by the spindle fibers which are attached at the centromere. Each CHROMATID is pulled to opposite sides of the cell Each side has a full complement set of CHROMOSOMES (DNA). Spindle Fibers

4. Telophase The SPINDLE begins to disintegrate and the NUCLEAR ENVELOPE begins to reform around each set of chromosomes. At this time, each side prepares to become a new DAUGHTER cell, with the same DNA and kind of chromosome as the PARENT cell. The chromosomes re- establish themselves into CHROMATIN and the nucleoli re-appear. Telophase Nuclear Envelope Chromatin Spindle Fibers

Cytokinesis Division of the cytoplasm – begins in ANAPHASE and continues throughout telophase. A PLASMA MEMBRANE begins to form between the two nuclei, as a ring forms and begins to constrict the cell at its EQUATOR. Two DAUGHTER cells are formed that are genetically IDENTICAL

mitosis Doing it all again, and again, and again (that’s why it is called a cycle) 46 Mitosis 46 The cells will begin to grow in interphase again when they reach a size that is too large or signaled they will divide again.

Cancer If the cycle is disrupted then the cell may continue to divide quickly and out of control. This may cause a tumor to form and may destroy the function of the organ. This is called cancer.

Interphase – Onion Root Tip

Prophase – Onion Root Tip

Metaphase – Onion Root Tip

Anaphase – Onion Root Tip

Telophase – Onion Root Tip

Cytokinesis – Onion Root Tip