The Cell Cycle and Mitosis: “You Complete Me” A process where one parent cell gives rise to two daughter cells- exact replicas of the original cell.
The Cell Cycle • Every cell goes through a process of growth, this is called the cell cycle. • Interphase is where DNA is synthesized (copied) in preparation of Mitosis.
The Cell Cycle Purpose: to replace dead or dying cells (repair) division of zygote into an embryo to allow an organism to grow and develop asexual reproduction
Interphase • It may not look like much is going on here, but there is a lot of activity because the cell must prepare for mitosis • Onion root tip (on left side), whitefish (on right side)
Interphase • protein synthesis • DNA synthesis/chromosomes are replicated • replication of other cellular structures
Mitosis • 4 phases:Prophase Metaphase AnaphaseTelophase • Cytokinesis (division of the cytoplasm) • one cell becomes two!
Mitosis: Prophase • Chromosomes condense and become visible • Nuclear envelope breaks down • Spindle begins to form • In animal cells centrioles move to poles • Onion root tip (top photo), whitefish (bottom photo)
Mitosis: Metaphase • Spindle fibers attach to the centromeres • Line up in the middle (the equator) of the cell • Onion root tip (top photo), whitefish (bottom photo)
Mitosis: Anaphase • The sister chromatids separate and are pulled to opposite sides of the cell by the spindle • Onion root tip (top photo), whitefish (bottom photo)
Mitosis: Telophase • Chromosomes now uncoil • Nuclear envelope reappears and surrounds the chromosomes • Onion root tip (top photo), whitefish (bottom photo)
Mitosis: Telophase Cytokinesis • The cytoplasm and all its contents are divided between the 2 daughter cells (cytoplasmic division)
Daughter Cells • The 2 daughter cells are exact replicas of the original parent cell • they are clones • have the exact same genetic make-up as the parent cell. • mitosis = cell division
Can you identify these stages? A B D C Answers: A. Telophase B. Prophase C. Cytokinesis D. Metaphase
Summary • One parent cell begins the journey through the cell cycle and 2 new identical daughter cells emerge from one cycle.
Mitosis occurs regularly in tissues that require new cells continuously such as skin cells, hair follicles, the lining of the digestive tract and in a newly fertilized egg (zygote).
This process is important as it allows for an organism to grow and develop over its lifespan and replenishes dead or dying cells in certain tissues.
The cells that result are identical to the original cell. There are no genetic differences. So skin cells make skin cells. But if you reproduce this way (paramecium, ameba) what kills one of you will kill all of you.