Week4 Assignment 1

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INTRO TO INFO SYSTEMS

Mitosis and the Cell Cycle

Kenneth Jones

1/20/2013

The objective of this exercise is to understand the phenotypic features during phases of the cell cycle and bean cells used as a model cell type.


INTRODUCTION
THE CELL CYCLE DESCRIBES A SERIES OF ORDERED AND DISTINCT CELLULAR STAGES LEADING TO DIVISION AND REPLICATION. STAGES OF THE CELL CYCLE ARE CALLED INTERPHASE, MITOSIS, AND CTYOKINESIS. INTERPHASE INCLUDES THREE PARTS. THE FIRST IS THE G1 PHASE OR GAP PHASE. THIS IS THE PHASE BETWEEN THE COMPLETION OF MITOSIS AND THE BEGINNING OF DNA SYNTHESIS. THEN THE S PHASE, OR THE SYNTHESIS PHASE, WHERE THE CELL COPIES ITS CHROMOSOMES, OCCURS. THE LAST PART OF INTERPHASE IS CALLED G2 AND REPRESENTS THE TIME BETWEEN SYNTHESIS AND THE START OF MITOSIS. THE NEXT PART OF THE CELL CYCLE IS MITOSIS AND CAN BE DIVIDED INTO FOUR PARTS. THE FIRST IS PROPHASE, DURING WHICH THE CHROMOSOMES CONDENSE INTO TWO CHROMATIDS, AND THE MITOTIC SPINDLES AT THE ENDS OF THE CELL APPEAR. THE NUCLEAR ENVELOPE ALSO BEGINS TO BREAK DOWN. THE NEXT IS METAPHASE WHERE THE CHROMOSOMES LINE UP ON THE METAPHASE PLATE. AFTER THIS, ANAPHASE OCCURS. DURING THIS PHASE, THE SPINDLE FIBERS ATTACH TO THE KINETOCHORES OF THE CHROMOSOMES AND PULL THE CHROMATIDS TO OPPOSITE ENDS OF THE CELL. THE LAST PART OF MITOSIS IS CALLED TELOPHASE. DURING TELOPHASE, THE MITOTIC SPINDLES BREAK DOWN AND THE CHROMOSOMES BEGIN TO UNCOIL. TWO NEW NUCLEAR ENVELOPES APPEAR AROUND BOTH SETS OF CHROMOSOMES. AFTER MITOSIS, THE CELL FORMS A CONTRACTILE RING DURING A PHASE CALLED CYTOKINESIS. THE RING IS MADE OF ACTIN FILAMENTS AND SURROUNDS THE CELL LIKE A BELT. THE CONTRACTILE RING CINCHES THE CELL AND DEEPENS THE GROOVE CALLED A CLEAVAGE FURROW. THIS EVENTUALLY DIVIDES THE CELL IN TWO LEAVING TWO NEW DAUGHTER CELLS. Materials and Methods

First, root tips from a bean were prepared by germinating for a week, prior to the experiment. Root tips were rinsed with tap water, placed in a...
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