Cell Division Examination

Cell division examination is made possible by phase contrast microscopy. With phase contrast illumination, staining is no longer required and thus allowing you to view cells in live motion. Cell division, especially meiosis, is fascinating to learn about as it’s the one responsible for genetic variety in offspring and maintaining cellular stability during environmental changes.

Cell Division and Meiosis
In cell division, a parent cell splits into two or more daughter cells. Meiosis is one process in which cell division occurs. In meiosis, the parent cell is a diploid eukaryotic cell and the daughter cells are haploid cells referred to as gametes.

The Phases in Meiotic Cell Division
There are several phases involved in meiotic cell division and they are interphase, prophase, metaphase, anaphase, telophase, and lastly, cytokinesis.

Interphase – This is one phase which meiosis and mitosis have in common. This is a preparatory phase and can be divided into three steps. In Growth 1 or G1, protein synthesis occurs and as such, cells are quite active in this stage. In Synthesis or S, replication of genetic material takes place. And in Growth 2 or G2, cells simply continue to grow in size.

Prophase – A number of stages make up prophase in meiosis. The first, leptotene, is where single chromosomes start to group together inside a cell’s nucleus. In the second stage, zygotene, homologous chromosomes pair up with each other. In the third stage, pachytene, chromosal crossover occurs. In diplotene, the pairs start to gradually separate. A fraction of DNA transcription takes place, too. In diakinesis, several things occur: the disappearance of nucleoli, disintegration of nuclear membrane, and formation of meiotic spindle. The final stages are collectively known as synchronous processes and it is in this step that centrioles move to attach themselves to chromosomes. All in all, this is meiosis’ longest phase.

Metaphase – Pairs of homologous chromosomes simply start moving together.

Anaphase – Homologous chromosome pair-ups separate and go to opposite poles of the cell. Cells start to elongate, preparing for division later on.

Telophase – Centromeres arrive at their given destination. The spindle network breaks up, and daughter cells are now born, with equal number of chromosomes but all of which containing a pair of chromatids. Nuclear membranes develop for each

Cytokinesis – This is the final stage of Meiosis 1. In plant cells, the cell wall is formed and in animal cells, the cell membrane is completed.

In Meiosis 2, the process simply becomes inversely proportional.

Cell Division Examination with a Microscope
Bright field illumination will not work with this type of activity since it’s not capable of making your sample visible without staining them first. Staining however requires killing of cells and with their death no meiosis will naturally take place.

As such, your options are somewhat limited. Dark field microscopy is affordable but cannot provide ideal image resolution and clarity. Electron microscopy is ideal but expensive. A good compromise however is phase contrast illumination. Although you might need to spend for a small amount of money for a phase contrast set to attach to your microscope, it’s a worthwhile investment to have, especially if you like studying invisible microorganisms, cells, and tissues.

Phase Contrast Microscopes
In 1934, Frits Zernike, a Dutch physicist, invented phase contrast microscopy. His achievement was awarded the Nobel Prize for physics in 1953. In phase contrast microscopy, differences in phases are transformed into amplitude variations that are visible to the naked eye. Also, the numerical aperture or NA of your microscope’s condenser is decreased by the annular ring.

How to Set Up Phase Contrast Illumination for Your Microscope
A phase contrast kit may be purchased for use with standard optical microscopes. A typical kit would consist of several objective lenses, phase condenser lens, and a centering telescope. The objectives will generally allow you to view the specimen with different magnification ranges and under bright field illumination or under normal light and without phase contrast.

Start by focusing on your specimen at bright field. Next, adjust your condenser’s height to find the ideal image resolution. Then, fix the condenser turret for phase contrast and the chosen objective lens. Remove the specimen afterwards.

Remove one of the eyepieces inserted in your microscope and replace it with the centering telescope. The screw is for focusing the telescope. Looking through it will show you a pair of rings. If they’re not aligned with each other, turn the screw to make them so. After achieving alignment, you can take the centering telescope off and return the eyepiece lens in its original place.

Return the specimen on the stage as well. When you peek through the eyepiece of your microscope, you can already view it with phase contrast illumination. Keep in mind however that every change of objective lens will require going through the entire process once more.

For more information, please visit http://www.phase-contrast-microscope.com