The Cell Cycle: A closer look! Biology 12

Funny?

Review (from last Class):

Which stage is longest?

Interphase Aka the resting phase (but not really…) Essentially, the cell is in between divisions and is carrying out maintenance activities of the cell Made up of 3 sub-phases: G1 phase S phase G2 phase

Interphase: G1 phase 1st growth phase Cell mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities, such as synthesising proteins

Interphase: S phase Synthesis stage DNA is copied or replicated Two identical copies of DNA Original DNA

Interphase: G2 phase 2nd Growth Stage Occurs after DNA has been copied All cell structures needed for division are completed (e.g. centrioles) Both organelles & proteins continue to be synthesized

Mitosis Aka karyokinesis Division of the nucleus Only occurs in eukaryotes Made up of 4 phases: Prophase Metaphase Anaphase Telophase

Mitosis: prophase Early prophase: Late prophase: Centrioles: make spindle fibres and move towards opposite plates Chromosomes shorten and thicken (now visible under a microscope) Late prophase: Centrioles reach poles Nuclear membrane (envelope) & nucleolus start to disappear

Mitosis: Metaphase Spindle fibres attach to centromeres Sister chromatids (doubled chromosomes) line up at equator (middle of cell) Guided by spindle fibers

Mitosis: Anaphase Centromeres divide in two Spindle fibers contract and pull sister chromatids towards opposite ends of cell (pole) Each pole (future daughter cells) will have an identical set of chromosomes

Mitosis: telophase Sister chromatids at opposite poles Spindle disassembles Nuclear membrane forms around each set of sister chromatids Nucleolus reappears Chromosomes loss their distinct outlines reappear as chromatin

In pictures: Prophase Metaphase Anaphase Telophase

Cytokinesis: Means division of the cytoplasm Division of cell into two, identical halves called daughter cells Would this happen the same way in plants and animal cells? Why or why not? In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell

Cytokinesis Cleavage furrow in animal cell Cell plate in animal cell Cleavage furrow is when the cell membrane pinches off

IPMATC Helpful hint? Interphase Prophase Metaphase Anaphase Telophase Cytokinesis IPMATC

Amimation: http://www.youtube.com/watch?v=AhgRhXl7w_g&feature=fvsr

To do: Mitosis colouring sheet Labelling sheet Nelson Bio 11 Book