Mitosis vs Meiosis: Key Differences, Processes, and Functions

Mitosis vs Meiosis: Key Differences, Processes, and Functions

Mitosis vs Meiosis: An In-Depth Analysis and Review

Task: Present a concise comparison between Mitosis and Meiosis.

Response

Preface
In the medical or scientific field, the precise origin of meiosis is inadequately elucidated in the chapter on eukaryotic history. The subject has always been a matter of contention, since the process of meiosis is essential for the perpetuation of the sexual life cycle. Meiosis, having developed from the mechanism of mitotic cellular division, has four main steps. The intricate intricacy of Meiosis has presented a challenge to the meiotic genesis hypothesis proposed by Darwin. This article on mitosis vs meiosis has been written to elucidate the life cycle of an organism via the process of cell division. This article on mitosis vs meiosis elucidates the transfer of genes from the mother cell to the daughter cells.

Cell Cycle

This article discusses mitosis vs meiosis within the context of the eukaryotic cell, which undergoes several phases during its existence, collectively referred to as the cell cycle. During the synthesis phase of the cell cycle, there are two distinct phases known as G1 and G2. The synthesis step is often represented by the letter S. The stage of cell division characterized by the replication of genetic material is designated as phase M.

G1 stage — During this phase, the cell prepares for division, resulting in observable metabolic changes. Subsequent to a designated interval, the cell becomes fully prepared for division and progresses to the next phase of synthesis, S. The transition of the cell from the gap 1 stage to the synthesis stage is referred to as the restriction point.

S stage - During the synthesis stage, the genetic information, namely the DNA, is replicated. Subsequent to this procedure, each chromosome inside the cell nucleus will consist of two sister chromatids.

G2 stage - During this interval, the cellular components are meticulously organized for division after the synthesis phase.

M stage - During this phase, both cellular division and nuclear division occur. Cell division is referred to as cytokinesis, whereas nuclear division is called mitosis.

The fundamental distinction between Mitosis and Meiosis

The process of cellular division via mitosis results in the formation of two daughter cells. The resulting daughter cells will contain the same number of chromosomes as the mother cell. Additionally, the daughter cells must carry the same kind of chromosomes that the mother cell had. Mitosis is the process by which the nucleus divides into two identical nuclei.

In the instance of meiosis, the process commences with two parental cells and culminates in the formation of four daughter cells. During meiosis, the chromosome count is halved compared to that of the mother cell. This mechanism of cellular division occurs only in multicellular eukaryotes that reproduce sexually.

Meiosis: A Comprehensive Examination

This research on mitosis vs meiosis indicates that meiotic cell division transforms two parental cells into four daughter cells. The daughter cells have just half of the genetic information, since the chromosomes are halved from the mother cells. The cells that undergo this sort of cellular division are referred to as gametes. In the male organism, they are referred to as sperm, whereas in the female organism, they are termed eggs.

The process of meiosis involves the division of diploid cells, resulting in the formation of haploid gametes or sex cells. The whole process of cellular division in meiosis occurs via two sequential divisions of the cell and its nucleus. The phases may be referred to as Meiosis I and Meiosis II. Meiotic cell division may be categorized into nine distinct phases, as depicted below. Let us examine it in detail.

Meiosis Phase I

Interphase

• The first event in the interphase is the replication of genetic material. The process of duplication produces two sets of chromosomes that possess identical properties.
• A pair of centrosomes is formed outside the nucleus in the cytoplasm, each containing paired centrioles. These components are considered crucial for the occurrence of cellular division.
• Microtubules are formed from these centrosomes during interphase.

Prophase I
Prophase 1 is subdivided into five distinct phases.

1. Leptotene - During this phase, the duplicated genetic material begins to aggregate and condense.
2. Pachytene – Chiasmata are generated by the joining of crossing-over pairs of homologous chromosomes.
3. Diplotene - The homologous chromosomes begin to split. At this stage, the chromosomes remain attached at the chiasmata.
4. Diakinesis - In this phase, the separation of chromosomes progresses as shown in diplotene. The chiasmata are located at the terminal ends of the chromosomes at this phase.
5. Prometaphase 1 — This is the last phase of prophase 1. At this stage, the spindle machinery may be seen inside the cell. Chromosomes are connected to the spindle fibers via kinetochores.

During this phase, more cellular motions and metabolic processes occur, as shown below.

• The replicated genetic components would assume the form of the letter X in the English alphabet after the condensation process. The X-shaped genetic materials may be readily seen in a cell using a microscope.
• The chromatids generated during the duplication of genetic material are converted into two identical sister chromatids due to condensation.
• Subsequent to that phase, the whole chromosomes inside the cell undergo pairing, resulting in the conjunction of chromosome 1 and chromosome 2.
• Only via the process of crossing over or recombination is a short segment of genetic information exchanged across chromosomes.
• At the conclusion of Prophase 1, the nuclear membrane disintegrates, allowing the chromosomes to become liberated inside the cell.
• Subsequently, the meiotic spindle facilitates the movement of chromosomes by establishing connections via microtubules.

Metaphase I
The metaphase plate in the cell displays the bivalents or homologous chromosomal pairs arranged in a double row. The paired chromosomes are organized in a seemingly random manner due to the arbitrary positioning of the spindle apparatus poles relative to the metaphase plate.

• The chromosomes generated during prophase 1 are positioned oppositely, with the border serving as the cell's center.
• The meiotic spindle facilitates the movement of centrioles to opposing poles.

At this step, a solitary chromosome attaches to the meiotic spindles.

Anaphase I

Following the procedure established in metaphase I, the bivalent chromosomes continue to migrate apart and become separated.
In contrast to mitosis I and mitosis II, the bivalent chromosomes remain associated throughout Meiosis I.
Telophase I

• Similar to the preceding phase of Anaphase I, the chromosomes persist in their separation towards opposing poles.
• Ultimately, the requisite collection of chromosomes is gathered at the opposing poles.
• The chromosomes generated during the process disperse, and two new membranes for distinct nuclei begin to form.
• During Anaphase I, the chromosomes persist in their separation, migrating towards opposing poles.
• Ultimately, the requisite collection of chromosomes is gathered at the opposing poles.
• The chromosomes generated during the process disperse, and two new membranes for distinct nuclei begin to form.

Cytokinesis
In the concluding phase of meiosis, cytokinesis occurs, resulting in the formation of two distinct cells. Meiosis I facilitates the process of reduction. The haploid cells produced get a perfect copy of the chromosomes from the parental cells.

Meiosis Phase II

The phases involved in the cell division process of Meiosis II are analogous to those in mitosis. The only difference between the two is the quantity of chromosomes. The chromosome count in Meiosis II is effectively half that of mitotic cell division. The objective of genetic variety is accomplished during cell division by the effective exchange of DNA during Meiosis I between bivalent chromosomes. The disorganized configuration of both paternal and maternal chromosomes during Meiosis I and the unpredictable alignment of bivalent chromatids in Meiosis II contribute to genetic diversity.

Prophase II

• During this phase, the resulting daughter cells get a single set of 23 chromosomes.
• The chromosomes condense and assume the shape of the letter X to facilitate division or distribution among the daughter cells.
• Subsequent to this process, the membrane of the daughter cell disintegrates, allowing the chromosomes in the daughter cells to become liberated.
• The components of the meiotic spindle begin to reemerge as the centrioles replicate.

Metaphase II

• During this phase, the chromosomes of the resulting daughter cell align along the equatorial plane after cellular division.
• The centrioles in the daughter cells would be located at opposing poles.
• The sister chromatids are anchored to the meiotic spindle fibers originating from the opposing poles of the daughter cells.

Anaphase II

• The chromatids are pushed towards the opposing poles of the daughter cells. The meiotic spindle executes this pull.
• Upon the separation of chromatids, the daughter cells get distinct sets of chromosomes.

Telophase II and Cytokinesis

• In the last phase of meiosis II, the chromosomes are positioned at the two opposing poles.
• In contrast to the chromatids, the whole configuration of chromosomes is organized at the poles of the daughter cells.
• Following these developments, two distinct daughter cells are formed, culminating in cytokinesis by the formation of a cellular membrane between them.
• Cytokinesis occurs when these cells become physically separated from one another.
• The procedure will yield four daughter cells, each with a haploid set of chromosomes.

We trust that you have thoroughly familiarized yourself with the principles of meiotic cellular division by reviewing the preceding portion of this paper on mitosis vs meiosis.

Mitosis: A Comprehensive Overview
During mitotic cell division, a parent cell divides into two daughter cells. The produced daughters would be quite similar and congruent to one another. The division occurs by dividing the genetic material into two identical and analogous groups inside the nucleus. Most cell division in the human body occurs via the process of mitotic cell division. Mitosis, in a biological context, is a eukaryotic cell division process that produces daughter cells from a single mother cell during the synthesis phase. The whole process of mitotic cell division in an animal cell is finished within one hour. The mitotic apparatus segregates the sister chromatids and other cellular components inside the parental cell. Karyokinesis refers to the division of the nucleus in the parental cell, whereas cytokinesis denotes the subsequent division of the whole cell at the later stage of cellular division. The process of cell division is finished to produce two daughter cells only once cytokinesis occurs.

In the majority of species, asexual reproduction occurs by mitotic cell division. The first creation of the cell occurs by the fusing of two gametes, or haploid cells, which carry just half of the genetic material. The resulting cell after the union will be referred to as the diploid zygote. Subsequent to the mitotic division of the zygote, the growth of the organism is facilitated. Upon complete maturation of the organism, the significance of mitosis becomes confined to the replacement of existing cells, the unregulated formation of tumors, and the repair of injuries.

Cellular division by mitosis is prevalent and may be categorized into five distinct phases: prophase, prometaphase, metaphase, anaphase, and telophase.

To populate an organism's body with new cells, mitotic cellular division is used.

Prophase
Initial Prophase
As it represents the first phase of cellular division, the fundamental metabolism of the cell undergoes alterations. The cell begins to exhibit noticeable alterations in the structure and properties of the organelle. As a prelude to cellular division, the chromosomes prepare for the division processes. Prior to chromosomal segregation, the mitotic spindles begin to emerge. A cell may be deemed ready for division if the ribosome-producing component degrades inside the cell.

Late Prophase
This phase is sometimes referred to as prometaphase. At this stage, the mitotic spindle formed during early prophase attaches to the chromosomes and further organizes them for division. Following the condensation of chromosomes, the nuclear membrane begins to disintegrate. Subsequently, the chromosomes are drawn to the extreme periphery by the mitotic spindle.

Metaphase
The formed spindles position the chromosomes at the cell's equatorial plane. The chromosomes would be aligned linearly along the cell's equator. The chromosomes align parallel to the metaphase plate. The microtubules also bind to the kinetochore of each chromosome.

The cell evaluates its progress and organizes chromosomes along the metaphase plate by attaching microtubules to kinetochores before to the onset of anaphase.

Anaphase
During this phase of cellular division, the identical chromatids are separated from one another. Upon separation, they go toward the opposing ends of the poles. The advancement will follow the sequence shown below. Kindly examine them thoroughly.

• During this phase of cellular division, the condensed chromosomes are separated and drawn toward the opposing poles of the cell.
• The microtubule organelles become apparent inside the cells, subsequently attaching to the chromosomes and initiating their separation from the centriole. During this process, the poles get separated, resulting in the cells seeming somewhat elongated.

The motions occurring during Anaphase are facilitated by motor proteins located along the microtubule tracks. During the process of mitosis, both chromosomes and microtubules move in conjunction with the microprotein.

Telophase
As the cell progresses into telophase, the division process nears its conclusion. During this phase, complete cytokinesis occurs, and the daughter cells restore their typical morphology. The whole process of telophase is detailed in the section below. Let we examine.

• The mitotic spindle organelle begins to manifest and functions as a foundational component.
• Subsequently, the nuclear membrane begins to reemerge during this phase. The nuclear membrane and nucleoli begin to manifest as part of maturation.
• Subsequent to cellular motions and metabolic processes, the chromosomes, initially condensed, begin to decondense and revert to their filamentous structure.

We have now comprehended all the fundamental phenomena associated with the phases of mitotic and meiotic cellular division. The two daughter cells produced by mitotic division contain around 46 chromosomes, identical to those in the parent cells. During meiosis, gametes or haploid cells are produced, resulting in daughter cells that each have a total of 23 chromosomes. Sperm and egg cells are classified as haploid cells.

The contrast between the processes of Mitosis and Meiosis
You now possess a comprehensive understanding of the metabolic alterations occurring during mitosis compared to meiosis in cellular division. Let us now examine the distinctions between the cellular divisions of mitosis and meiosis.

                                 Table 1: Variations in mitosis vs meiosis.
Meiosis' Evolution from Mitosis
It may be inferred that the first cell formed in the universe was haploid, containing a single pair of chromosomes, which would have been transmitted to additional cells by the process of mitotic division. In the ancient age, several primary cell types, such as fungi and protists, underwent mitotic cell division. Diploid cells emerged on Earth after many decades of evolution. The first diploid cell on Earth emerged either by endomitosis or cell fusion. Upon further investigation, it may be seen that the process of mitosis significantly influences the history of living ecosystem. All living cells on Earth are prokaryotic homologs derived from mitotic cell division in eukaryotic cells. The greater resemblance between mitosis and meiosis suggests that meiotic cells have originated from cells that underwent mitotic division. Mitotic cell division is prevalent among eukaryotic cells, but meiosis occurs only in creatures that reproduce sexually.

References

Bakhoum, S. F., Kabeche, L., Murnane, J. P., Zaki, B. I., & Compton, D. A. (2014). DNA-damage response during mitosis induces whole-chromosome missegregation. Cancer discovery, 4(11), 1281-1289.

Dominguez-Brauer, C., Thu, K. L., Mason, J. M., Blaser, H., Bray, M. R., & Mak, T. W. (2015). Targeting mitosis in cancer: emerging strategies. Molecular cell, 60(4), 524-536.

Maiato, H., Gomes, A. M., Sousa, F., & Barisic, M. (2017). Mechanisms of chromosome congression during mitosis. Biology, 6(1), 13.

McIntosh, J. R. (2016). Mitosis. Cold Spring Harbor Perspectives in Biology, 8(9), a023218.

Minocherhomji, S., Ying, S., Bjerregaard, V. A., Bursomanno, S., Aleliunaite, A., Wu, W., ... & Hickson, I. D. (2015). Replication stress activates DNA repair synthesis in mitosis. Nature, 528(7581), 286-290.

Ohkura, H. (2015). Meiosis: an overview of key differences from mitosis. Cold Spring Harbor Perspectives in Biology, 7(5), a015859.

Schellhaus, A. K., De Magistris, P., & Antonin, W. (2016). Nuclear reformation at the end of mitosis. Journal of molecular biology, 428(10), 1962-1985.

Vicente, J. J., & Wordeman, L. (2015). Mitosis, microtubule dynamics and the evolution of kinesins. Experimental cell research, 334(1), 61.