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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).