Mitosis is a continuous process to separate copied chromosomes into two daugheter cells through prophase, metaphase, anaphase and telophase ( Yuki, et al, 2012). On the other hand Kanyemba, (2020) defines mitosis as a mode in which cells can channel by dividing into two copies, during this process for each one of the resulting cells must have an accomplished copy of the genetic information in the parental cell and places one copy of each into each daughter cell. It is responsible for shaping of the mitotic spindle that is responsible for chromosome movement, separation of chromatids and the distribution to the dividing daughter cells ( Schatten, 2013).
The aim of this practical was to be able to define mitosis as well as to examine an onion root tip under a microscope and observe different mitotic stages that occur in the cells of onion root tips. Ultimately identify chromosomes at various stages of mitosis and make sketches of mitotic stages observed.
MATERIALS AND METHOD
Stained onion slides were made by cutting an onion bulb that was rooted in water by cutting 3 roots near the base of the bulb. After that 2 mm of the root tip was cut at the bottom and placed in a petri dish with a pasteur pipette.Addition of a small puddle of 1 M HCL and the root tip was left to stand for 4 minutes. Later it was removed from HCL with forceps and placed on a slide, then it was covered with 2 drops of 1 % toluidine blue and then a drop of water was added and a cover slip applied. The cover slip area was squashed in order to spread the root tip. The slide was viewed under the microscope to observe mitotic stages in individual cells chromosomes and sketches of mitotic stages were made. At this time the preparation of epidermis specimen followed where a drop of water was placed in the middle of a microscope slide, peeled off a thin epidermis from the inner surface of an onion and placed on the slide which was covered with a cover slip.
DISCUSSION AND CONCLUSION
Mitosis include five stages known as prophase, prometaphase, metaphase, anaphase and telophase in which chromosome condesation, alignment of chromosomes at central plate and movement to opposite poles take place by ( Schatten , 2013). Key events such as sister chromatid separation is mediated by the anaphase during this stage centromes start splitting and sister chromatids begin to move towards the opposite poles of the cell ( Peters , 2002). According to Nagasaka, et al, (2016) they found that formation of mitotic chromosomes involves both compaction and resolution of sister chromatids the compaction occur during prophase and prometaphase in prophase spindle fibres commence. Not only but also chromatid resolution start at the commencement of prophase and each chromosome is comprised of two sister chromatids as shown by the results above. Interphase the DNA in the cell is copied in preparation for cell division resulting in two identical chromosomes it has outside nucleus containing a pair of centrioles.Likewise telophase the single cell pinches in the middle to form separate daughter cells as shown in the results containing full set of chromosomes, besides metaphase here chromosomes line up neatly, centricles are opposite.
To sum up it is stated that all somatic cells undergo stages of mitosis many times through the lifespan and stated that chromosomes in one stage of mitosis and during mitotic stages will be seen these five stages differ from one another.Apart from thisit is seen th interphase consist of 3 substages.During interphase chromosomes become denser and visible under the microscope, metaphase chromosomes move. And the last stage of mitosis is telophase where chromatids decondense and form chromatin again.It should be noted that mitosis and it’s stages were defined leading to the practical being fruitful.Nonetheless the limitation of this practical was that although cell shape and nucleus were observed the shape of chromosomes were not seen with further magnification.
- Kanyemba, S. (2020) Cell Molecular Biology and Genetics.
- Nagasaka, K.,Roberti, M.J., Ellenberg, J. & Hirota,T. (2016) Nature of cell Biology. [online]. Available from doi:10.1038/ncb3353.
- Peters, J. (2002) Molecular cell. [online].Available from doi:10.1016/S1097- 2765(02)00540.3.
- Schatten, H. (2013) Brenner’s Encyclopedia of Genetics.2nd ed [online]. Available from doi: 10.1016/B978-0-12-374984-0.009621-1.
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