The document discusses the cell cycle and differentiation. It describes the three main stages of the cell cycle as interphase, mitosis, and cytokinesis. Interphase is broken down into Gap 1, synthesis, and Gap 2 phases. Mitosis consists of prophase, metaphase, anaphase, and telophase. Cytokinesis is the final stage where the cell physically divides. Differentiation is when unspecialized cells become specialized cell types by turning on and off parts of their DNA. Stem cells can become any cell type while progenitor cells are somewhat specialized.

1. Cell Cycle & Differentiation Chapter 3 Unit 1

2. The Cell Cycle A set of events that occur during a cell’s lifetime From the time a cell is “born” until it divides Cycle is repeated for each cell Includes: Growth Preparation Division

3. The Cell Cycle

4. The Cell Cycle Consists of three major stages: Interphase* Mitosis* Cytokinesis *Each of these are broken into several distinct phases

5. The Cell Cycle Interphase Cell’s spend about 90% of the cycle in here Broken down into three phases Gap 1 Synthesis Gap 2

6. Interphase Gap 1 AKA “Growth” 1 Cells in this phase are growing in size Producing lots of ATP Dividing and reproducing cell organelles

7. Interphase Synthesis Cells in this phase are copying all the DNA found in the nucleus Synthesis is referring to the building of new DNA molecules Necessary to ensure that both cells that result from division have 100% of DNA

8. Interphase Gap 2 AKA “Growth” 2 Cells in the phase are checking to make sure their DNA has been replicated correctly Check to make sure organelles are copied

9. The Cell Cycle Assuming everything is ready at the G2 phase, the cell will proceed to division Cell division in humans is called mitosis Has four phases Prophase Metaphase Anaphase Telophase

10. Mitosis Prophase Pro- means first DNA thickens into chromosomes Remember, it has been replicated. Look like X’s Each side of the X is called a chromatid Nuclear membrane dissolves

11. Prophase

13. Mitosis Metaphase Meta- means middle Spindle Fibers form Attach to centromere of chromosome Move chromosomes to cell’s equator Centrioles found at opposite ends of cell

14. Metaphase

15. Mitosis Anaphase Spindle Fibers shorten, pulling chromosomes in half Sister chromatids split apart Chromatids move toward opposite sides of cell ***Chromatids are now called chromosomes

16. Anaphase

17. Mitosis Telophase Chromosomes reach the cell’s poles Two new nuclei form…one around each set of chromosomes at opposite ends Chromosomes unwind Spindle fibers dissolve

18. Telophase

19. Cytokinesis The final stage of cell division Literally means “cytoplasm divides” Cell pinches in half The “pinch” is called a cleavage furrow

20. Differentiation Humans are conceived when a sperm and egg unite, forming a single-celled zygote Zygotes are unspecialized When we are born, we have more than 260 specialized cell types How??? Differentiation

21. Differentiation Cells specialize by differentiating into certain cell types They turn off parts of DNA that they don’t need Use only the parts of DNA that are needed to become a specific cell *Cells that are specialized generally can’t change and become other cell types

22. Differentiation Stem Cells Unspecialized cells that can can become ANY type of cell in the body Stem cells found in every organ in body Stimulated to divide when… Growth is needed Damage needs to be repaired

23. Differentiation When a stem cell divides… Two cells are produced through mitosis One cell is a new stem cell (unspecialized) One cell is called a progenitor cell Somewhat specialized Will divide many more times, with each daughter cell become more and more specialized *Cells “decide” to become specialized at the end of the G1 phase of cell cycle See Page 69 in textbook!!!

24. Apoptosis Defined as programmed cell death Happens at the end of G1 in cell cycle Occurs for many reasons Sculpting organs from overgrown tissue in the fetus Removes webbing between fingers as fetus Destroys skin cells following a sunburn