Mitotic Cell Cycle Lab Report

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Background to the Mitotic Cell Cycle
All living organisms have several mechanisms that allow cell survival/ life continuity and reproduction. A major role in eukaryotic survival is attached to the cell cycle. It comprises of 2 major phases and in a typical human cell it lasts for approximately 24 hours. The first phase is identified as synthesis (S) phase whereas the second is mitotic (M) phase. Between those phases, 2 gap phases occur (G1 and G2). During the gap phases time delay happens, thus allowing cells to grow and develop. Therefore, they last for 15 hours in total, 11 hours for the first gap phase and 4 hours for the second. S-phase together with both gap

Two centrosomes move to the opposite side of the cell, allowing/providing the development of the mitotic spindle. Also, nucleus starts to fall apart, releasing chromatin. It is subsequently condensed into visible chromosomes, composed of sister chromatids. During prometaphase, the nucleus completely collapses. It enables the attachment of chromosomes to the formed mitotic spindle and the movement of chromosomes. In metaphase, chromosomes become aligned throughout the metaphase plane, an imaginary line located in the midway between two opposite poles of the

As a result of chromosomal separation, daughter chromatids are formed. They move in different directions, toward the poles. Furthermore, chromosomes in anaphase have the highest possible condensation, which helps to reform the nucleus in the subsequent phase. The last phase of mitosis is telophase. It brings the reappearance of nuclear envelopes which outcome in the formation of two nuclei. Additionally, mitotic spindle disintegrates and chromosomes are uncoiled into chromatin, returning the cell to the interphase structure. Even though mitosis is finished with telophase, the final cell segregation occurs at cytokinesis. It starts before telophase and divides the cytoplasm of the cell, therefore making two daughter cells with the genetically identical nucleus.

The aim of the practical was to observe the sample of the onion root tip under the microscope and to count cells in different mitotic phases. After, students were expected to calculate mitotic index of observed sample and compare it other provided samples.

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