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Onion Root Mitosis http://www.microscopyuk.org.uk/mag/artnov04macro/jronionroot.html Allium root tip by Joseph C. Rossi It is common to see photomicrographs of onion root cells when demonstrating how cell division takes place in plants. Onions have larger chromosomes than most plants and stain dark. The chromosomes are easily observed through a compound light microscope. Phases of plant cells division: 1) Interphase is considered the first and last stage of plant cell division. It is the stage in which the cell is growing in size and replicating its DNA in preparation for division. The nucleus is apparent. 2) Prophase. During Prophase the nuclear envelope starts to break down and all the chromosomes start to coil up in the center of the cell. The cells pictured below are located in the apical meristem of the onion root. The apical 3) Metaphase is the middle stage at which point all the chromosome pairs meristem is an area of a plant where cell line up in the center of the cell along spindle fibers that pull to either side division takes place at a rapid rate. of the cell. 4) Anaphase. The spindle fibers become shorter and pull each chromosome pair apart to the opposite ends of the cell. 5) Telophase. The final stage of cell replication.The nuclear envelope is reformed. Cytokinesis takes place. A new cell wall is created down the center and two daughter cells are formed. 1) Interphase 4) Anaphase All photomicrographs captured at approximately 160X 2) Prophase 3) Metaphase 5) Telophase with a Nikon D1X Lighting technique: Kohler illumination Equipment used to photograph the onion root: Nikon Optiphot microscope Nikon Plan Apochromatic 40X objective Nikon Apochromatic sub stage condenser I am a Student at Rochester Instutuite of Technology studing in the Biomedical Photographic Communications Department. email : [email protected] Return to index of articles by students on the 'Principles and techniques of photomacrography' course, November 2004, Biomedical Photographic Communications (BPC) program at the Rochester Institute of Technology (RIT). Article hosted on Micscape Magazine (Microscopy-UK). Whitefish Mitosis A section of whitefish blastula at 400x Introduction Why are whitefish blastula used to study mitosis? The blastula is an early stage of embryo development and rep period in the organism's life when most of the cells are constantly dividing. Moreover, the dividing cell have very easily seen chromosomes, so its easy to find lots of cells in each stage of mitosis.Human chromosomes on the oth are not clearly visible at higher power magnification. So, for student purposes, whitefish blastula are used. Interphase Whitefish blastula cells in interphase The three phases of Interphase G1 Phase Growth: the cell grows in size and carry out their normal day to day activities. S Phase Prior to mitosis, the cell readies itself by duplicating its chromosomes and other cellular contents. The chromosom stage are dispersed and not visible using a light microscope. Before DNA synthesis, each of the cell’s chromosom of one chromatid. After DNA synthesis, each of the cell’s chromosomes consist of 2 genetically identical sister c attached at the centromere. G2 Phase The cell prepares the enzymes and machinery for mitosis. Prophase Whitefish blastula cells in early prophase During early prophase, the chromosomes condense, making them distinguishable when using a light microscope. The nuclear envelope disperses.During late prophase, the nucleoli disappear and the mitotic spindle apparatus ass mitotic spindle will consist of microtubules that extend from pole to pole. Metaphase Whitefish blastula cells in metaphase: the cell on the left is in early metaphase, the cell on the right in late m The mitotic spindle has attached to the centromere of each chromosome and moves them through the "dance of m Note that the centromeres of each chromosome are aligned at the equator of the cell and the telomeres (ends of th chromosomes) drift away from the equator. Anaphase A whitefish blastula cell in anaphase During anaphase the mitotic spindle apparatus pulls the sister chromatids of each chromosome apart by attaching centromere and then pull the chromatids to each pole of the cell. Note that the telomeres of each chromosome po the cell’s equator. Telophase A whitefish blastula cell in telophase + cytokinesis Chromosomes begin to disperse. Spindle fibers disperse. Cytokinesis begins--formation of daughter cells. In anim whitefish, a cleavage furrow, a contractile ring of muscle like fibers, pinches the cell into two. The nuclear envel again around the nuclei. Whitefish Mitosis Practice The photomicrographs below show sections of whitefish blastula. The blastula is an early stage of embr development, and represents a period in the organism's life when most of the cells are dividing consistently. Practice locating each of the stages of mitosis in the following photomicrographs. Each picture contains at least one cell at each stage of mitosis (and some stages are represented by multiple cells).