Chapter 9 Page 244 CELLULAR REPRODUCTION

 Cells grow until they reach their size limit, then their either stop growing or divide.  Limitation for cell size: ratio of surface area to volume  Surface area = area covered by plasma membrane CELLULAR GROWTH

 Volume = space taken up by inner contents of cell  Try a little math CELLULAR GROWTH

 Small cells vs. large cells  Fill out your notes CELLULAR GROWTH

DIAGRAM OF A CHROMOSOME

 Chromosome: a structure made of DNA and proteins on which genes are located  Chromatid: half of a chromosome  Centromere: a region joining 2 chromatids A FEW DEFINITIONS….

 Made of DNA and proteins all coiled up  Found in the nucleus of eukaryotic cells  Contain genes – thousands of genes!  When a cell is not dividing, the chromosomes are all tangled up (chromatin)  Before a cell divides, the DNA replicates CHROMOSOMES

 The 2 sister chromatids pair up into Homologous chromosomes  similar in size, shape, function, and genetic content  Each chromatid comes from each of your parents  Each species has a certain number of chromosomes CHROMOSOMES CONTINUED…

THE CELL CYCLE A repeating sequence of cellular growth and division during the life of an organism

 Cells reproduce for two reasons  Growth and repair THE CELL CYCLE

 Cell Cycle: 3 stages  Interphase  Mitosis  Cytokinesis THE CELL CYCLE

 Interphase  Most of a cell’s life  Cell grows, develops, matures and duplicates its DNA and organelles to prepare for mitosis THE CELL CYCLE

 G1 phase  First growth phase  90% of a cell’s life  Cell is growing and carrying out all normal functions  Muscle and nerve cells never move past this point  If a cell dies, it never replicates THE CELL CYCLE

 S phase  Synthesis phase  DNA is synthesized (duplicated)  DNA is in the form of chromatin THE CELL CYCLE

 G2 phase  Second growth phase  Cell is preparing for the division of its nucleus  Cell takes inventory and makes sure it has everything it needs to divide THE CELL CYCLE

 Mitosis vs. Binary Fission THE CELL CYCLE

MITOSIS This is when the cell divides Each daughter nuclei will have the same number of chromosomes as the original cell 4 steps (PMAT) Prophase Metaphase Anaphase Telophase

MITOSIS Mitosis happens CONSTANTLY in your body to repair tissues and to replace old, dying cells ONLY in your body cells (somatic cells)

MITOSIS Prophase Longest phase of mitosis Chromatin condenses into chromosomes (little x’s) Nuclear envelope dissolves

MITOSIS Metaphase Chromosomes line up along the equator of the cell Spindle fibers attach to chromosomes

MITOSIS Anaphase Chromosomes are pulled AWAY from each other by spindle fibers (sister chromatids separate) They move to opposite sides of the cell

MITOSIS Telophase Chromosomes arrive at opposite poles Nuclear envelope reforms Chromosomes relax, chromatin reforms

MITOSIS  Cytokinesis  Dividing of the cytoplasm  Results in two identical daughter cells with identical nuclei  In animal cells, a furrow forms that pinches the cytoplasm

MITOSIS  Cytokinesis  In plant cells, a cell plate forms  Cell walls form on either side of cell plate

MITOSIS  Cytokinesis  In bacterial cells, the duplicated DNA attaches to the cell membrane  As the cell membrane grows, the DNA is pulled apart

CELL CYCLE REGULATION The normal cell cycle is regulated by cyclin proteins The timing/regulation of the cell cycle is important to the health of all organisms

CELL CYCLE REGULATION  Checkpoint #1  G1 Checkpoint  Am I large and healthy enough to divide?  Muscle cells and nerve cells never divide and go into a resting state (G0 phase)

CELL CYCLE REGULATION  Checkpoint #2  G2 checkpoint  Did my DNA replicate properly?

CELL CYCLE REGULATION  Checkpoint #3  Mitosis checkpoint  Did I replicate correctly?

CELL CYCLE REGULATION  Abnormal cell cycles can lead to cancer – the uncontrolled growth and division of cells  Cells are not responding to the normal cell cycle control mechanisms (checkpoints are broken)  Crowds normal cells  Loss of cellular function  Cell divides faster

 Mutations are changes in DNA that control the production of proteins that control cell growth  Tumor: A mass of cancer tells within normal tissue CELL CYCLE REGULATION

 Benign tumor: cancer cells remain at the original site  Malignant tumor: Cancer cells are spreading to other tissues  Metastasis: The spread of cancer from the original site CELL CYCLE REGULATION

 Carcinogens: substances that are known to cause cancer  Tobacco, radiation  Apoptosis: programmed cell death  Webbed fingers, leaves in fall CELL CYCLE REGULATION

 Stem Cells: unspecialized cells that can grow into specialized cells under the right conditions  Embryonic stem cells  Adult stem cells CELL CYCLE REGULATION