Suppose that your hand was made of one cell. What would happen if that cell were to die?

Warm-Up Questions After you’ve answered them, talk with the person sitting next to you! What happens if a cell in our hand dies? Do all the cells die? Do we lose our hand? How many cells are really in our bodies? What does our body do to replace these dead cells? What is this process called? Trillions

Cellular Reproduction

Review: why are cells small? What was that ratio we talked about? What’s good, big or small SA:V? Transport.

How does this apply to cell division? Once a cell reaches its size limit, it must divide. This is also the way the cell reproduces! Growth Repair (of injuries) Each time a cell goes through the cell cycle, it becomes two cells. Today: Mitosis (Asexual Reproduction) Friday: Meiosis (Sexual Reproduction)

The Cell Cycle Three stages Interphase – cell growth/development, replication of DNA, preparation for division 90% of time spent here! Mitosis – nucleus and nuclear material (chromosomes) divide Cytokinesis – cytoplasm divides Prokaryotes divide by binary fission As few as 8 minutes, up to a year. Typically 12-24 hours in us. Binary fission – we’ll come back to this.

Phases of Interphase Gap 1 (G1) – cell is growing and preparing for division. immediately after the cell divides Some cells exit and do not divide again Synthesis (S) – cell copies its DNA for division Chromosomes – structures that pass on genetic material Chromatin – relaxed form of DNA in nucleus Gap 2 (G2) – cell prepares for nuclear division Checkpoint Start here for 1st period! Muscle and nerve cells.

Prophase Chromatin condenses into chromosomes Terminology – Sister Chromatids Centromere Nuclear membrane disintegrates/Nucleolus disappears Spindle apparatus of microtubules begins to form (Centrioles) Mitosis – give me an example Busiest stage. What does it mean to condense? (we can see shaped like an X) Nucleolus disappears Spindle apparatus include microtubules! Centrioles/aster fibers.

Metaphase Sister chromatids are pulled by motor proteins along the spindle apparatus towards the center of the cell Short stage Metaphase plate

Metaphase

Anaphase Sister chromatids are pulled apart via shortening of microtubules Centromeres Chromatids are moved towards the poles of the cells with the help of motor proteins

Anaphase

Telophase Chromosomes arrive at the end of the cell and de-condense Nuclear membrane reforms/nucleolus reppears Spindle apparatus disassembles Nucleolus reappears

Cytokinesis Division of the cytoplasm – results in two cells Microfilaments pinch the cytoplasm Plant cells – cell plate forms

“Normal” Cell Cycle Proteins called cyclins bind to CDKs (cyclin-dependent kinases) to proceed with various activities of the cell cycle. Used as quality control checkpoints That we talked about before

Cancer Cancer – uncontrolled growth and division of cells Failure to regulate cell cycle Due to mutations—changes in the DNA Carcinogens – substances that are known to cause cancer Why might risk of cancer increase with age? Because the longer you live, the more likely you are to have a mutation

Apoptosis Programmed cell death – a controlled process Fingers and toes Leaves falling What other reasons would cells have for doing this? Stopped here! Remind them to think about reasons why cells would stop dividing…

Stem Cells Unspecialized cells that develop under the “right” conditions Embryonic stem cells – 100-150 cells after fertilization before specialization “Adult” stem cells – used for repair

Human Mitosis Dance - maybe Groups of 7 (assigned by Mr. Koons) One narrator Parts that must be represented (by people, props, narration, etc.): All four stages of mitosis plus interphase Chromosomes (in various forms) Centrioles/mitotic spindle Centromeres Nuclear envelope Tell Mr. Koons your song choice! We’ll assume you’re in a cell…

Before You Present Articulate Roles Clarify any props Anything else you’d like to share