The Tragic Ending. Cell Division in Eukaryotes As you are sitting in class now, your cells are...
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Transcript of The Tragic Ending. Cell Division in Eukaryotes As you are sitting in class now, your cells are...
The Tragic Ending
Cell Division in Eukaryotes• As you are sitting in class now, your
cells are growing, dividing and dying.
Cuts and bruises are healing
RBC’s are being produced in your bones at a rate of 10-15 million per sec.Muscle cells are
get larger when you exercise.
Worn out cells in the palm of your hand are being replaced.
Cell Division
How do you grow?
The number of cells in your body is increasing!!
How Do Cells Increase In Number?
• In your body, all of your cells, except your sex cells, divide by a process called mitosis.
• In mitosis, a parent cell divides to form two identical daughter cells.
• The daughter cells have the same contents of the parent’s nucleus.
Cell Cycle
• Most of a eukaryotic cell’s life is spent in a phase called interphase.
• Interphase consists of three stages: G1, S, and G2 – G1: a time of growth and maintenance– S: DNA is replicated: this commits the
cell to divide– G2: more growth as the cell prepares
for division
.
Cell Cycle • Mitosis: division of the nucleus: – Four phases: prophase,
metaphase, anaphase and telephase.
• Cytokinesis: division of the cytoplasm
• After the cell divides into 2 identical daughter cells, the cycle starts over again.
http://www.cellsalive.com/cell_cycle.htm
Cell Cycle
Interphase• Chromatin coils up into chromosomes
• A copy of each chromosome in the nucleus is produced
• These duplicated chromosomes are held together by a centromere.
• Cells that no longer divide are always in interphase.
Interphase
Mitosis in Animal Cells• A form of asexual
reproduction• The nucleus of a cell
divides, producing 2 nuclei that are identical to each other
• Has 4 phases: prophase, metaphase, anaphase, telophase
Prophase• Duplicated chromosomes become fully visible• Organelles called centrioles move to opposite ends of
the cell• The nucleolus and nuclear membrane disintegrate• Threadlike spindles stretch across the cell between
the centrioles
Prophase
Metaphase• Duplicated chromosomes line up across the
center, or equator, of the cell.
• Each centromere attaches to 2 spindle fibers
Metaphase
Anaphase
• Each centromere splits and the identical chromosomes separate and move towards opposite ends of the cell.
Anaphase
Telophase• Spindle fibers disappear
• Chromosomes uncoil and are harder to see
• A nuclear membrane forms around each mass of chromosomes
• A new nucleolus forms in each new nucleus
Telophase
Cytokinesis• The cytoplasm and its contents divide
into 2 individual daughter cells.
• Each daughter contains a nucleus and identical chromosomes.
Virtual Lab
• Cell Reproduction
• http://bio.rutgers.edu/~gb101/virtuallabs_101.html
Mitosis in Plant Cells• What’s Different?• Plant Cells do not have centrioles
• A cell plate forms between 2 new nuclei
• New cell walls form along the cell plate, and new cell membranes form inside the cell walls.
Plant Mitosis
"And do you, Michelle, take Andrew until mitosis do you part?"
Chromosomes
-The other two chromosomes, X and Y, are the sex chromosomes. The above picture of the human chromosomes lined up in pairs is called a karyotype.
-The 22 autosomes are numbered by size.