Student Goals Explain the purpose of cell division Identify the steps and events of each cell phase.

Cell Size Cell size is constrained by cellular needs for raw materials and the chemical properties of molecules. too big = can’t get enough matter and energy or get rid of chemical wastes too big = too many demands on DNA – things get out of control Sometimes, smaller is better Which nucleus is bigger? They are exactly the same size.

Life of a Cell Cells lining the esophagus live for 2-3 days Cells lining the small intestine live 1-2 days White blood cells may live for only 10 hrs, or for decades Red blood cells live less than 120 days Muscle cells live for years Nerve cells live for many years

Cell Life Most of the time that a cell is alive, it is busy growing, making molecules and using them. This is called Interphase (the time between mitotic divisions) The DNA is strung out in the nucleus, invisible. (chromatin) When the cell reaches its size limit, it gets ready to divide in two in a process called mitosis. Before that can happen, the DNA and all the cellular organelles are replicated during interphase.

Life Cycle of a Cell Interphase – growth, increase in size, and synthesis of organelles and molecules G1 S G2 Mitosis - Cell division Prophase Metaphase Anaphase Telophase Cytokinesis

The Big Picture One cell becomes two Each with the same number of chromosomes as the Parent cell

The Big Picture- 2 Before PROPHASE the chromatin is replicated (copied). During PROPHASE it condenses into chromosomes. Each chromosome has a replicated twin = sister chromatids. These are the 46 chromosomes in a human cell as mitosis begins.

Chromatin > Chromosome > Chromatids Chromatin, Chromosomes, and Chromatids are all the same– named differently depending on the stage. Chromatin Chromosome Chromatids Differences between Chromatin/Chromosomes/Chromatids http://www.youtube.com/watch?v=s9HPNwXd9fk

1. Prophase Pro = pre (before) 2. Metaphase Meta = middle 3. Anaphase Ana = apart 4. Telophase Telo = two 5. Cytokinesis Cyto = cell, kine = move

Mitosis: What does it look like? Identify each stage from the pictures

Mitosis: What does it look like?

Mitosis: What does it look like? Examine Allium root tips under the microscope and identify the parts.

Mitosis: What does it look like?

Quiz yourself Check out this website! (biologycorner.com) For a REVIEW and practice quiz! http://www.biologycorner.com/bio1/cellcycle.html Practice Quiz on Discovery Education http://school.discoveryeducation.com/quizzes6/muskopf/mitosis1.html