Cell Growth and Division

Cells perform many functions from respiration to making new cell organelles At some point they need to divide

How many chromosomes does an organism have? Bacteria – 1 Most other organisms have many more

When a cell divides, it must make a copy of all of its chromosomes in its nucleus

Cell Cycle Interphase: phase in which cells spend most of their life Normal state of a cell, cell grows, cells does “its job,” synthesizes DNA, and prepares for division

Cell division Continuous process Nerve, muscle cells no longer divide—always in interphase Skin cells, actively divide— have more complex cell cycle

Mitosis Cells divide in 2 steps: first the nucleus divides and then the cytoplasm divides Mitosis: nucleus divides to form 2 identical nuclei

Mitosis Each nucleus contains same # and type of chromosomes as the original Cytoplasm of the parent cell then undergoes division

Overview of Mitosis http://www.hybridmedicalanimati on.com/anim_mitosis.html http://www.cellsalive.com/mitosis .htm http://www.cellsalive.com/cell_cyc le.htm

Steps of Mitosis Interphase – not part of mitosis, nucleus is visible , chromosomes not visible, but dividing,

Interphase, cont. – chromosomes divide but remain attached at a region called the centromere

Chromatid – each piece of the replicated chromosome attached at the centromere is called a chromatid

Prophase – chromosomes visible – double stranded attached at the centromere, nucleolus and nuclear membrane disappear,

Prophase, cont. – centrioles move to opposite ends of cell, spindle fibers begin to stretch across the cell

Metaphase – double stranded chromosomes line up across center of cell, centromere becomes attached to a spindle fiber

Anaphase – centromere divides and two strands of each chromosome separate and move to opposite ends of the cell

Telophase – centrioles and spindle fibers start to disappear, chromosomes stretch out and become harder to see,

Telophase, cont. –nuclear membrane begins to form around each mass of chromosomes, new nucleolus appears in each new nucleus

Cytokinesis – not part of mitosis, cytoplasm separates and two new cells are formed

Products of Mitosis Mitosis makes two identical cells from one division Mitosis makes body cells

Animal Cells v. Plant Cells in Mitosis Have centrioles and spindle fibers Cytoplasm pinches in to form the new cells No centrioles, only spindle fibers Cell plate forms between the two new nuclei New cell walls form along the cell plate Animal Cells Plant Cells

https://wikispaces. psu https://wikispaces.psu.edu/display/Biology/Mitosis-Cell+Cycle+Regulation