1 / 20

Cell Reproduction

Cell Reproduction. Honors Zoology. Reasons cells divide. Growth and development zygote to adult Replace old cells – lining of digestive tract and skin Repair damaged tissue – heal injuries Reproduction – make offspring GRRR!. 1 cell to 90 trillion. Most animals start out as a zygote

gwen
Download Presentation

Cell Reproduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cell Reproduction Honors Zoology

  2. Reasons cells divide • Growth and development zygote to adult • Replace old cells – lining of digestive tract and skin • Repair damaged tissue – heal injuries • Reproduction – make offspring • GRRR!

  3. 1 cell to 90 trillion • Most animals start out as a zygote • A zygote is formed by the union of an egg and a sperm.

  4. Mitosis • The zygote divides to form genetically identical daughter cells. • They divide to form more genetically identical cells.

  5. The Process of Cell Replication Interphase – 3 phases - DNA is called chromatin in interphase G1- Most of the life of the cell. - When they do their ‘work’ S - Time when conditions are right and the signal comes for DNA synthesis to occur. G2 – Organelles reproduce in preparation for Mitosis

  6. DNA Replication • During S phase of interphase a set of enzymes separate the DNA double helix and allow each side to serve as the template for synthesis of a new complementary strand of DNA. • The old molecule separates in half, gets new nucleotides paired with it to produce new DNA molecules that are ½ old and ½ new.

  7. How it Works

  8. The Good News – You do not have to memorize all of that!What to know… • DNA has 2 strands with complementary nucleotides. • Adenine pairs with Thymine and Guanine pairs with Cytosine. • Each strand is replicated in opposite directions. • DNA Polymerase is the enzyme that places the nucleotides and catalyzes their bonds.

  9. What to know continued… • There are several other enzymes involved that unzip and untwist the original strand, hold it open, place RNA primers, hook/repair broken nucleotide bonds, keep it from twisting too tight, and replace the ending segments. • Actually, just know that DNA Polymerase acts in concert with several other enzymes. • The replicated strands remain attached at the centromere – as chromatids

  10. Prophase • After DNA is replicated and repaired, it begins to coil into chromosomes. • They consists of 2 identical copies of the DNA called chromatids. • The chromatids are held together at the centromere which has a protein called the kinetochore. • The kinetochore attaches to spindle fibers during mitosis.

  11. All wrapped up and let’s dance! • DNA is not available for transcription during this time. • While the chromosomes were wrapping up, spindle fibers were growing out of the 2 centrosomes, which usually contain centriolesin animals.

  12. Getting attached and dragged to the dance floor – line dance! • As spindle fibers form the nuclear membrane breaks apart and beads up to be divided between the daughter cells. • The spindle fibers attach to the kinetochore and the chromosome moves back and forth until it settles in the middle on the metaphase plate.

  13. Metaphase • When the Chromosomes are lined up in the middle.

  14. Anaphase • The chromatids separate at the centromere. • The chromatids move down the spindle fibers in opposite directions toward the centrosomes. • The spindle fibers without chromatids push the centrosomes apart making the cell oval shaped.

  15. Telophase • The opposite of prophase. • The chromatids – now chromosomes uncoil into chromatin. • The nuclear membrane reforms. • Spindle fibers disappear.

  16. Cytokinesis – division of the cytoplasm • A cleavage furrow forms where the metaphase plate was. A ring of actin fibers circles the cell and interacts with other proteins to cinch the cell in half. • The infolded edges of the membrane meet and fuse.

  17. The daughter cells • Are genetically identical. • They are clones. • If the cells separate when a zygote under goes mitosis, they are identical twins.

  18. Control • The cycle of cell division and growth is controlled by the rise and fall of protein in the cell, especially cyclin. • Cyclinworks with other proteins called cdk’s to initiate cell division.

  19. Programmed Cell Death • Called apoptosis • Necessary for normal growth and development. Without it you would hae webbed fingers and a tail!

  20. Now… • Use the pop beads to model mitosis for 2 chromosomes – red and yellow. • Your other supplies include yarn, string, beads, magnetic pieces, and two sheets of paper.

More Related