Microscopic Examination Of Blood Cells Biology Essay

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Nucleic acids are found in all living organisms. They are the molecules that carry genetic information in all cells [Carpi 2OO3].This experiment was first started in 1869 by Johannes Friedrich Miescher to find the location of Deoxyribonucleic acids {DNA} and Ribonucleic acids {RNA} in a cell [Friedrich Miescher, 2O1O].

Background of white blood cells

White blood cells help to protect the body in various ways against diseases. The bone marrow is the part of the body that is responsible for producing white blood cells. There are a total of 5 different types of white blood cells, which can be classified into 2 different groups, granulocytes and agranulocytes. Granulocytes are white blood cells with multi-lobed nucleus and grainy appearance of the nucleus whereas agranulocytes have a single, large nucleus. Granulocytes are usually eosinophils, basophils and neutrophils. Agranulocytes are lymphocytes and monocytes [Liang 2O1O].

Aim of experiment

The aim of this experiment is to show the location of the DNA and RNA in a cell, and to be able to classify white blood cells into 2 categories, which are granulocytes and agranulocytes.


The hypothesis of this experiment is that Methyl-green pyronin and RNase will stain the slide green as RNA is degraded. And methyl-green pyronin and DNase will stain the slide red as DNA is degraded. This will show that DNA will be found within the nucleus and RNA will be found within the cytoplasm.

Materials and methods used



Carnoy fixative



MGP{Methyl Green-Pyronin}



Frosted slides

Cover slip



Preparing the blood smear

Firstly, two frosted-end microscope slides were thoroughly cleaned by dipping into 95% ethanol and then wiped with Kim wipes. Next, aseptic methods were used to obtain the blood. After washing the hands and drying them, the ring finger should be cleaned with sterile alcohol and the finger should be lanced with a sterile lancet. Next, the finger should then be squeezed and the first drop of blood should be wiped away. The lancet was not used more than once and was disposed off into the sharps container after being used. Next, a blood smear was being made by squeezing the finger again and placing a drop of blood near one end of the slide. Then, another slide held with its edge held at an angle of 3 0 degrees to the first slide and the blood was slowly being spread across the slide. This was repeated for the second slide and both slides were allowed air dry.

Staining the blood smear

Followed by that, the blood smear was immersed into Carnoy fixative for ten minutes, fixing it and stopping all molecular activities. After that, the slide was immersed into 95% ethanol for a few seconds to dehydrate the smear. Then, the smear was rinsed with distilled water for two minutes and the water was allowed to drain off. After that, the two slides were labelled RNase + MGP, and MGP. The slide labelled as RNase + MGP was placed in a 0.1%aqueous solution of RNase at 37 degree Celsius for 3 0 minutes. All staining and enzyme treatments were taken place in coplin jars and the coplin jars were placed in water baths. The slides were removed or placed into the jars by the use of forceps. After 30 minutes, the slide treated with RNase was rinsed with distilled water for a few seconds and then both the slides were placed into the coplin jar containing Methyl green-pyronin for a further 30 minutes. After 30 minutes, each slide was rinsed in distilled water for 3 seconds in a coplin jar. The slides were then drained of water and the back of the slides were then dried with Kim wipes and allowed to air-dry in a near vertical position.

Preparation for microscopic examination

Lastly, a drop of permount was added and cover slips were placed onto the slides, doing so slowly so as to prevent the formation of air bubbles or artefacts. The blood smear was then observed under the microscope of dry high power [X4O] and high-power oil immersion [X1OO]

Precautions taken while doing the experiments

The precautions taken during the experiment were that aseptic techniques were used to obtain the blood sample. The lancet was used only once and it was disposed off into the sharps container after being used. When spreading the blood sample, it was done smoothly so as to have an even layer of blood on the slide so that it can be observed properly. The slide was allowed to air dry properly after being rinsed in distilled water. The cover slip was put on slowly so as not to collect air bubbles or artefacts The excess fluids were gently being pressed out with a paper towel.


The result of this experiment is that the slide labelled MGP + RNase was stained green and the slide labelled MGP was stained both green and rose-red. The slide labelled MGP + RNase was stained green and after being observed under a microscope, it is shown that the green portion of the cell is mainly in the nucleus, whereas on the other slide, the green stain was within the nucleus as well with a tinge of rose-red stain in the nucleus, with the cytoplasm of the cell being stained rose-red. After being observed under a microscope of high-oil immersed power, it can be seen that the white blood cells have 2 major appearances, which are of a single nucleus and that of a multi-lobed nucleus. The results can be seen from the tables on the next page, which will illustrate the results better.


By comparing the results and the hypothesis, it can be seen that they are very similar. The hypothesis is that Methyl-green pyronin and RNase will stain the slide green as RNA is degraded. This can be seen in the results, where the RNA has been degraded and the DNA is the only thing remaining. As MGP stains DNA green, it is the reason why the slide is stained green.

The next hypothesis is that DNA will be found within the nucleus and RNA will be found within the cytoplasm. From the results, we can see that only the nucleus portion of the white blood cell is being stained green, whereas in the other slide, the green portion is also within the nucleus, whereas the surrounding cytoplasm is stained rose-red. Since methyl-green pyronin{MGP} stains DNA green and RNA rose-red, it can be used to locate DNA and RNA in a cell. And RNase is an enzyme which can be used to degrade RNA, which means that when it is used on the blood smear, the RNA in the blood cell will be degraded, leaving behind only DNA. Thus, when we use MGP on the slide treated with RNase, only a green stain was observed and not both colours. This proves the point that the DNA is located within the nucleus and the RNA is located mainly in the cytoplasm. Lastly, after observing being observed under the microscope, it can be seen that the white blood cell can be separated into 2 groups, one with a single large nucleus, and one with a multi-lobed nucleus.


In conclusion, the hypothesis was proven to be correct, the aims were achieved and the experiment was a success. From the results shown it can be safely concluded that MGP will stain DNA green and will stain RNA rose-red. From the results shown, it can also be concluded that DNA is located within the nucleus, whereas RNA is located mainly in the cytoplasm. This can be seen from the stains of the Methyl-green pyronin. It can also be seen that white blood cells are separated into 2 major groups, agranulocytes and granulocytes, as observed under the microscope. Lastly, for the experiment to be a success, the precautions should be taken.