Difference between Mitosis and Meiosis & their Comparisons
Difference Between Mitosis and Meiosis: We are aware that all organisms, even the largest came from the single-celled. Growth and development are the two characteristics of the cell. Cell division is also very important for living organisms, Mitosis and Meiosis are the two types of cell division the difference between mitosis and meiosis is that in mitosis two daughter cells are formed each with the same number and type of chromosomes as the parent cell whereas in meiosis of chromosomes as the parent cell refers to the cell division which forms four daughter cells each with half the number.
Difference Between Mitosis and Meiosis
The difference between Mitosis and meiosis is that mitosis type of cell division takes place in asexual reproduction whereas meiosis takes place in sexual reproduction. Also, there is a difference in stages, in mitosis karyokinesis(a division of the nucleus) involves four stages, that is, Prophase, Metaphase, Anaphase, and Telophase whereas meiosis involves two sequential cycles of nuclear and cell division called meiosis I and meiosis II. Meiosis I involve the following four events, that is, Prophase I, Metaphase I, Anaphase I, Telophase I, and Meiosis II involves the following four events, that is, Prophase II, Metaphase II, Anaphase II, Telophase II. The other difference is based on the number of cells, the number of daughter cells, no. of chromosomes, spindle fibers, etc. are codified below-
| Differences | Mitosis | Meiosis |
| Type of Reproduction | Asexual | Sexual |
| Genetically | Similar | Different |
| Crossing Over | No, crossing over cannot occur. | Yes, the mixing of chromosomes can occur. |
| Number of Divisions | One | Two |
| Pairing of Homologs | No | Yes |
| Mother Cells | Can be either haploid or diploid | Always diploid |
| Number of Daughter Cells produced | 2 diploid cells | 4 haploid cells |
| Chromosome Number | Remains the same. | Reduced by half. |
| Chromosomes Pairing | Does Not Occur | Takes place during zygotene of prophase I and continues up to metaphase I. |
| Creates | Makes everything other than sex cells. | Sex cells only: female egg cells or male sperm cells. |
| Takes Place in | Somatic Cells | Germ Cells |
| Chiasmata | Absent | Observed during prophase I and metaphase I. |
| Spindle Fibres | Disappear completely in telophase. | Do not disappear completely in telophase I. |
| Nucleoli | Reappear at telophase | Do not reappear at telophase I. |
| Stages | Prophase, Metaphase, Anaphase, Telophase. | (Meiosis 1) Prophase I, Metaphase I, Anaphase I, Telophase I; (Meiosis 2) Prophase II, Metaphase II, Anaphase II, and Telophase II. |
| Karyokinesis | Occurs in Interphase. | Occurs in Interphase I. |
| Cytokinesis | Occurs in Telophase. | Occurs in Telophase I and in Telophase II. |
| Centromeres Split | The centromeres split during anaphase. | The centromeres do not separate during anaphase I but during anaphase II. |
| Prophase | Simple | Complicated |
| Prophase | The Duration of the prophase is short, usually of few hours. | Prophase is comparatively longer and may take days. |
| Synapsis | No Synapsis | Synapsis of Homologous chromosomes takes place during the prophase. |
| Exchange of Segments | Two chromatids of a chromosome do not exchange segments during prophase. | Chromatids of two homologous chromosome exchange segments during crossing over. |
| Discovered by | Walther Flemming | Oscar Hertwig |
| Function | Cellular reproduction and general growth and repair of the body. | Genetic diversity through sexual reproduction. |
| Function | Takes part in healing and repair. | Takes part in the formation of gametes and maintenance of chromosome number. |
Overview of Mitosis
Mitosis is the process by which a cell divides to create two identical daughter cells. The process of mitosis occurs in somatic cells(somatic cells are the cells that are not sex cells) also this process of cell division helps to repair the cell. Most cells generated from such cell division last for a few days to a few weeks (The exception is brain cells which last for the whole life).
The phases of Mitosis involve four stages:
- Prophase: In this phase, Chromosomal material condenses to form compact mitotic chromosomes. Chromosomes are seen to be composed of two chromatids attached together at the centromere. Centrosome which had undergone duplication during interphase begins to move towards opposite poles of the cell. Each centrosome radiates out microtubules called asters. The two asters together with spindle fibers form mitotic apparatus.
- Metaphase: The complete disintegration of the nuclear envelope marks the start of the second phase of mitosis, hence the chromosomes are spread through the cytoplasm of the cell. All the chromosomes coming to lie at the equator with one chromatid of each chromosome connected by its kinetochore to spindle fibers from one pole and its sister chromatid connected by its kinetochore to spindle fibers from the opposite pole. This plane of alignment is called metaphase alignment.
- Anaphase: At the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids, now referred to as daughter chromosomes of the future daughter nuclei, begin their migration towards the two opposite poles.
- Telophase: Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. A nuclear envelope develops around the chromosome clusters at each pole forming two daughter nuclei.
Significance of Mitosis
- Production of diploid daughter cells having identical genetic complements.
- The growth of multicellular organisms is due to mitosis.
- The significant contribution of mitosis is cell repair.
Overview of Meiosis
The other type of cell division is Meiosis. In this process single cell divides twice to produce four daughter cells having half the genetic material. The only cells that go through meiosis are gametes, or sex cells (sperm in men and eggs in women). The phases of Meiosis involve two sequential cycles, that is, Meiosis I and Meiosis II.
Meiosis I: This phase is grouped into the following four stages:
- Prophase I: Prophase I is longer than the mitotic prophase and is further subdivided into 5 substages, leptotene, zygotene, pachytene, diplotene, and diakinesis. The chromosomes begin to condense and attain a compact structure during leptotene. In zygotenethe pairing of homologous chromosomes starts a process known as chromosomal synapsis, accompanied by the formation of a complex structure called synaptonemal complex. A pair of synapsed homologous chromosomes form a complex known as bivalent or tetrad. At the pachytene stage, the crossing over of non-sister chromatids of homologous chromosomes occurs at the recombination nodules. The chromosomes remain linked at the sites of crossing over. Diplotene marks the dissolution of the synaptonemal complex and the separation of the homologous chromosomes of the bivalents except at the sites of cross-over. The X-shaped structures formed during separation are known as chiasmata. Diakinesis is marked by the termination of chiasmata and assembly of the meiotic spindle to separate the homologous chromosomes. The nucleolus disappears and the nuclear envelope breaks down.
- Metaphase I: The bivalents align at the equatorial plate and microtubules from the opposite poles attach to the pairs of homologous chromosomes.
- Anaphase I: The two chromosomes of each bivalent separate and move to the opposite ends of the cells. The sister chromatids are attached to each other.
- Telophase I: The nuclear membrane reappears and is followed by cytokinesis. This gives rise to a dyad of cells.
Meiosis II: This phase is grouped into the following four stages:
- Prophase II – It immediately sets off after the cytokinesis when the daughter cells are formed. The chromosomes begin to condense accompanied by the dissolution of the nuclear membrane and the disappearance of the Golgi apparatus and ER complex.
- Metaphase II – The chromosomes are connected to the centriole poles at the kinetochores of sister chromatids through the microtubules. They also get aligned at the equator to form the metaphase plate.
- Anaphase II – In this phase of meiosis II, there is a simultaneous splitting of the centromere of each chromosome and the sister chromatids are pulled away towards the opposite poles. As the chromatids move towards the poles, the kinetochore is at the leading edge with the chromosomal arms trailing.
- Telophase II – The chromosomes dissolve again into an undifferentiated lump and a nuclear envelope develops around it. Followed by cytokinesis, telophase II marks the end of meiosis. Four haploid daughter cells are formed as a result.
Significance of Meiosis
- Meiosis is the mechanism by which the conservation of a specific chromosome number of each species is achieved across generations.
- It also increases the genetic variability in the population of organisms from one generation to the next.