Mitosis and Meiosis

Mitosis and Meiosis

Part I

Objective

To understand and identify the mitosis’ cycle and the length of each stage.

Introduction

In eukaryotic organisms, cell division is an important aspect of their survival. The root tips of plants, particularly onions, are utilized for the studying of cell division. It is due to that onions are easy to cultivate, the tips are actively dividing, and their chromosomes are large. Therefore, the study will be carried on the root tips of onions at the region of cell division – the section between root cap and region of cell elongation.

Materials

1. Compound light microscope
2. Staining dye

• Glass microscope slide

1. Scalpel
3. Onion root tip

Method

The root tips of the onions were sliced into thin sections then mounted on the slides. Staining – to increase the visibility of chromosomes – and to cover with a coverslip was then done.

Results and Analysis

                        Fig. 1: Phases of Mitosis as seen under a compound microscope

Table 1

(Mandi & Biology, 2012)

To calculate the duration spent in each stage, the cell cycle will be used by applying the formula below:

            % of the cell cycle spent in this stage = (Number of cells in the given stage) / (total number of cells counted) × 100 

Table 2

Key: I – Interphase, II- Prophase, III- Metaphase, IV – Anaphase, V telophase, and VI- Cytokinesis

Fig. 2. Cell Cycle of mitosis’ phases

Discussion and Conclusion

From Fig.1, it is evident that each stage’s duration decreases as the mitosis process progresses. Interphase is the lengthiest as the cell prepares for mitosis – chromosomes and centromere, among others, start forming. In prophase, the second-longest stage, the membrane of the nucleus fragments, and the centrioles microtubule attach to the chromosomes. The shortest stage is telophase and cytokinesis. It is because the organelles are stable from the interphase stage; cytoplasm and membrane re-form.

Overall, mitosis serves to increase the number of somatic cells. The six segments are unique. In interphase, the centrosome is formed. Mitotic spindle form in prophase, chromosomes line up in the metaphase plate in the third segment, while in anaphase, sister chromatids are disconnected and travel to the centromeres. In telophase, the spindles disappear, and finally, cytokinesis, chromatids become single-stranded (Newpath Learning 14).

The cells of the root tip regions are different. It is due to that, the ones in the region of elongation are bigger than the ones studied – from the region of division.

Part II

Meiosis is divided into two broad phases, Meiosis I and II. Both phases have four sub-phases, namely, prophase, metaphase, anaphase, and telophase.                                                             Fig 3. Meiosis Phases

Fig. 4: Meiosis I chromosomes changes

Fig. 5: Meiosis II chromosome changes

Meiosis’s purpose is to increase the number of gametes in eukaryotes that reproduce sexually. Metaphase, I and metaphase of somatic cells, are different because the former has homologous chromosomes, which have crossed-over. Concerning anaphase, I and anaphase of mitosis, the former’s homologous chromosomes are divided into full chromosomes, whereas the latter, the sister chromatids in the chromosomes are separated. The difference in these phases makes the meiosis and mitosis cells to be haploid and diploid, correspondingly.

Mitosis and Meiosis

Part I

Objective

To understand and identify the mitosis’ cycle and the length of each stage.

Introduction

In eukaryotic organisms, cell division is an important aspect of their survival. The root tips of plants, particularly onions, are utilized for the studying of cell division. It is due to that onions are easy to cultivate, the tips are actively dividing, and their chromosomes are large. Therefore, the study will be carried on the root tips of onions at the region of cell division – the section between root cap and region of cell elongation.

Materials

1. Compound light microscope
2. Staining dye

• Glass microscope slide

1. Scalpel
3. Onion root tip

Method

The root tips of the onions were sliced into thin sections then mounted on the slides. Staining – to increase the visibility of chromosomes – and to cover with a coverslip was then done.

Results and Analysis

                        Fig. 1: Phases of Mitosis as seen under a compound microscope

Table 1

(Mandi & Biology, 2012)

To calculate the duration spent in each stage, the cell cycle will be used by applying the formula below:

            % of the cell cycle spent in this stage = (Number of cells in the given stage) / (total number of cells counted) × 100 

Table 2

Key: I – Interphase, II- Prophase, III- Metaphase, IV – Anaphase, V telophase, and VI- Cytokinesis

Fig. 2. Cell Cycle of mitosis’ phases

Discussion and Conclusion

From Fig.1, it is evident that each stage’s duration decreases as the mitosis process progresses. Interphase is the lengthiest as the cell prepares for mitosis – chromosomes and centromere, among others, start forming. In prophase, the second-longest stage, the membrane of the nucleus fragments, and the centrioles microtubule attach to the chromosomes. The shortest stage is telophase and cytokinesis. It is because the organelles are stable from the interphase stage; cytoplasm and membrane re-form.

Overall, mitosis serves to increase the number of somatic cells. The six segments are unique. In interphase, the centrosome is formed. Mitotic spindle form in prophase, chromosomes line up in the metaphase plate in the third segment, while in anaphase, sister chromatids are disconnected and travel to the centromeres. In telophase, the spindles disappear, and finally, cytokinesis, chromatids become single-stranded (Newpath Learning 14).

The cells of the root tip regions are different. It is due to that, the ones in the region of elongation are bigger than the ones studied – from the region of division.

Part II

Meiosis is divided into two broad phases, Meiosis I and II. Both phases have four sub-phases, namely, prophase, metaphase, anaphase, and telophase.                                                             Fig 3. Meiosis Phases

Fig. 4: Meiosis I chromosomes changes

Fig. 5: Meiosis II chromosome changes

Meiosis’s purpose is to increase the number of gametes in eukaryotes that reproduce sexually. Metaphase, I and metaphase of somatic cells, are different because the former has homologous chromosomes, which have crossed-over. Concerning anaphase, I and anaphase of mitosis, the former’s homologous chromosomes are divided into full chromosomes, whereas the latter, the sister chromatids in the chromosomes are separated. The difference in these phases makes the meiosis and mitosis cells to be haploid and diploid, correspondingly.

Work Cited

Mandi & Biology. “Onion Root Tips Mitosis.” Mandi & Biology, 9 Mar. 2012, www.manditaylorjebe.wordpress.com/2012/01/09/onion-root-tips-mitosis/.

Newpath Learning, NewPath. Mitosis: Cell Growth & Division Science Learning Guide. NewPath Learning, 2014.

Work Cited

Mandi & Biology. “Onion Root Tips Mitosis.” Mandi & Biology, 9 Mar. 2012, www.manditaylorjebe.wordpress.com/2012/01/09/onion-root-tips-mitosis/.

Newpath Learning, NewPath. Mitosis: Cell Growth & Division Science Learning Guide. NewPath Learning, 2014.