Now Showing at a science lab near you! Limited engagement The Cell Cycle Now Showing at a science lab near you! Limited engagement

Directed by the nucleus A One Act Play Directed by the nucleus Produced by God

The Plot: one cell splits into two identical smaller cells. Purpose: 1. increase size of an organism 2. replace damaged cells

Starring DNA

The 3 faces of DNA Chromatin material – DNA as long strands Sister chromatids – DNA coiled tightly and taking on the form of the letter X Daughter chromosomes – Separated sister chromatids looking like the letter V

DNA (Deoxyribose nucleic acid) Model discovered by Watson & Crick Composed of 3 parts Sugar (deoxyribose) Phosphate 4 types of nucleotide bases Adenine Thymine Guanine Cytosine

Also starring Centrioles and Spindle fibers

Overview of the Cell Cycle

Scene One Interphase

Interphase The period of time between cellular divisions Time period for normal cellular metabolism Composed of 3 parts G1 S G2

G1 part of Interphase The first gap of Interphase Time period before the DNA is replicated Cell doubles in growth Cytoplasmic organelles replicate Time when the cell commits to cell division

S part of Interphase Time period of DNA replication DNA unzips and new nucleotide bases are laid down beside the original nucleotide bases Results in 2 identical DNA structures

G2 part of Interphase The second gap of Interphase Rapid cell growth Time period for synthesis of enzymes and structures (asters & spindle fibers) necessary for cell division Chromatin material checked for damage (repairs made if necessary)

3 types of spindle fibers Polar fibers – extend from centriole to centriole Kinetochore fibers – extend from centriole to centromere on a chromosome Asters – short fibers extending to the outside of the centrioles

Interphase Picture

One more review of the cell cycle

Mitosis Mitosis is part of the cell cycle, it is not the cell cycle The following 4 scenes are the stages of mitosis

Scene Two Prophase

Prophase Chromatin material coils so the chromosomes look short, thick, and the shape of an X (now called sister chromatids) Nuclear envelope begins to disintegrate

Prophase Centrioles begin moving apart and towards opposite poles of the cell Sister chromatids begin moving to the equator of the cell

Prophase Picture

Scene Three Metaphase

Metaphase Easiest stage to recognize! Kinetochore fibers pull sister chromatids so they are lined up at the equator of the cell

Metaphase Picture

Scene Four Anaphase

Anaphase Centromeres separate so the sister chromatids are no longer X’s but are now V’s (called daughter chromosomes) Kinetochore fibers pull daughter chromosomes to a centriole Centromeres travel ahead and the daughter chromosome arms travel behind (creating the V shape)

Anaphase Picture

Scene Five Telophase

Telophase Daughter chromosomes arrive at the opposite poles Daughter chromosomes unwind and are referred to as chromatin material again Spindle fibers disintegrate Nuclear envelope reforms around the chromatin material Cytokinesis occurs

Cytokinesis Division of the cells’ cytoplasm Different for animals and plants Animals – cell membrane pinches in to form a cleavage furrow and divides the cell at the center Plants – cell plate formed at equator of cell and cellulose is laid on each side to create new cell walls

Telophase Picture

Cytokinesis Picture

Cytokinesis Picture

One last look at the cell cycle

How well do you remember the stages of the cell cycle?