In order to observe a slice of an onion root in the process of mitosis first, I have completed a number of steps. First of all, I placed a slice of the root on a microscope slide, having stained this slice beforehand to make the chromosomes more visible. Then I used the lower power objective lens to focus the microscope on the slide and brought the root cells into focus. Having focused the microscope, I have observed the following changes:
Interphase. According to Stages of Mitosis (2019), during interphase, DNA is duplicated in preparation for mitosis – that is, for the following phases. There is not much to examine, and that is why I have moved on to the next stage.
Prophase. During that phase, as a result of further chromosome condensation, I have observed a ball of initially thin and later thicker and shorter strands appearing in the nucleus. Nucleolus and nuclear envelope are still visible in the early stages of prophase – by the end of it, they disappear.
Metaphase. The spindle fibers can be observed to draw the chromosomes to the nucleus cell center. What it does is helps to arrange a copy of one of the chromosomes for every new nucleus in the next stage.
Anaphase. In this phase, a uniform distribution of genetic material across the daughter cells is ensured. In the early anaphase, I observed the centromeres being rotated to the cell poles and the ends of the chromosomes to the cell center.
Telophase. During telophase, the chromosomes begin to de-condescence, and the chromosome matrix starts to become noticeable. The nuclear envelope appears, and the nuclei are restored. Simultaneously, in late anaphase and early telophase, a septum is made up in the cell center, which grows to the periphery and separates the cell into equal parts called daughter cells.
After that, I turned to the examination of whitefish blastula cells in the process of mitosis. The following stages during the different stages have been observed:
Interphase. The cell is about to enter into mitosis, and chromosomes are observed to look as threads in their structure.
Prophase. Proteins alongside DNA condense in the nucleus, known as chromatin. Consequently, chromosomes visibly condense due to the coiling of chromatin.
Metaphase. I have observed the chromosomes lining up due to mitotic spindle tension. The spindle takes all the chromosomes and puts them in the center of the cell, ready to divide.
Anaphase. Each pair of chromosomes is divided into two independent but identical chromosomes. After that, they can be seen pulled by the spindle’s force to the different poles of the cell.
Telophase: In the final stage, the genetic material transferred to the nucleus of the parent cell is divided into two daughter cells. Around each chromosome group, a nuclear membrane is formed – it separates nuclear DNA from the cytoplasm. After that, chromosomes are observed to separate and form chromatin.
When it comes to calculations that can be made in relation to processes of mitosis, these can be used in order to calculate necessary figures:
- Percentage of cells in a stage = (number of cells in a stage/total number of cells) x 100;
- The time that an onion root tip cell spends at each stage = (number of cells at each stage/total number of cells counted) x 720, where 720 minutes is the cell cycle for onion root tips;
- The percentage of time spent in each stage of the cell cycle = (total time in stage/total time).
In conclusion, I have registered the peculiarities of mitosis processes in the onion root and whitefish blastula. The main difference is that in onion root cells – plant cells – there is no cleavage furrow forming due to the rigid cell wall. However, what these two processes have in common is the active division due to the rapid growth of organisms. There was not necessarily anything new that I learned – rather, I have observed the basic occurrences of cell division in effect. Nothing could be done differently since I was a mere observer of the naturally happening processes.
Reference
Stages of mitosis (Cell division). (2019). Sciencing. Web.