The main difference between mitosis and meiosis is that at the end of mitosis, the chromosome number in daughter cells is equal to the number in the original cell (mother cell), whereas, in meiosis, daughter cells receive half the number of chromosomes from the mother cell.
The words mitosis and meiosis can be confused by some as they seem a bit alike. Both these processes denote the chromosome division followed by a cell division (cytokinesis). In mitosis, a single nuclear division (karyokinesis) and cell division take place, whereas in meiosis, two nuclear and cell divisions take place (meiosis I and meiosis II).
Key Terms
1. What is Mitosis
– Definition, Characteristics, Phases
2. What is Meiosis
– Definition, Characteristics, Phases
3. Difference Between Mitosis and Meiosis
– Comparison of Key Differences
Key Terms
Mitosis, Meiosis
What is Mitosis
Mitosis consists of five stages: prophase, prometaphase, metaphase, anaphase, and telophase and cytokinesis.
Prophase
Each chromosome in a prophase cell consists of two sister chromatids attached to one centromere. In this stage, chromosomes become more condensed and, therefore, can be seen under a light microscope. At this stage, mitotic spindle microtubules move the chromosome within the cell forms. The spindle grows out from a pair of centrosomes and grows towards the opposite end of the cell. However, this structure cannot be observed in some plant cells.
Prometaphase
Prometaphase starts with the degeneration of the nuclear membrane. Some spindle fibers are attached to the centromere regions of the chromosomes. Microtubules are attached to either side of the sister chromatids to kinetochores. Then the other end of these microtubules gets attached to the centrosome of the opposite poles.
Metaphase
In this phase, chromosomes are arranged along the center of the cell, metaphase plate as a single line.
Anaphase
After the metaphase connection between sister chromatids breaks down, the chromatids start to move in the opposite direction from each other, i.e., towards centrosomes. Special proteins called molecular motor proteins disassemble tubulin molecules in the spindle and generate force so that chromosomes are pulled towards the opposite poles.
Telophase
Once the chromatids move to the spindle poles, the chromatids are referred to as chromosomes. In the telophase, the nuclear membrane re-forms around each set of chromosomes and produces two distinct nuclei within the cell. Chromosomes also start to relax; therefore, the condensation disappears. Generally, telophase is followed by cytokinesis.
What is Meiosis
Meiosis is composed of two cell divisions: meiosis I and meiosis II. Meiosis I has five stages, prophase I, metaphase I, anaphase I, and telophase I. Furthermore, meiosis II also consists of five stages prophase II, metaphase II, anaphase II, and telophase II.
Meiosis I
Prophase I
The longest stage in meiosis I. This stage is subdivided into five stages as:
Leptotene: Chromosomes begin to condense, becoming visible.
Zygotene: Homologous chromosomes start to pair up while condensing, and a close association called synapsis occurs between them.
Pachytene: Chromosomes continue to shorten and thicken, and the synaptonemal complex becomes more noticeable.
Diplotene: Centromeres of the paired chromosomes move apart.
Diakinesis: Further condensation of chromosomes takes place.
Metaphase I
Homologous chromosomes are aligned along the metaphase plate. The microtubule from one pole attaches to one centromere, and the opposite end microtubule attaches to the other homologous pair of the chromosome.
Anaphase I
A homologous pair of chromosomes move towards the opposite ends from each other, i.e., towards the spindle end.
Telophase I
Chromosomes arrive at the spindle end and cytoplasm divide.
Meiosis II
As in prophase I of meiosis, prophase II starts with the thickening of chromosomes, the disappearance of the nuclear envelope and the formation of spindle fibers. Then in metaphase II, chromosomes arrange singly on the metaphase plate, and spindle fibers from two opposite centrosomes get attached to the centromeres. The new metaphase plate is rotated by 90o when compared to the metaphase I of meiosis I. During anaphase II, centromeres divide, and chromatids pull towards opposite ends. In telophase II, chromosomes relax, the nuclear envelope forms, spindle fibers disassemble, and finally, cytokinesis takes place, resulting in four daughter cells.
Difference Between Mitosis and Meiosis
Definition of Mitosis and Meiosis
Mitosis is a cell division method that produces two daughter cells that have an equal number of chromosomes to the mother cell and are identical to the mother cell. Meiosis is a cell division method that produces four daughter cells that have half the number of chromosomes from the mother cell and are genetically different from the mother cell.
Discovery
Mitosis was discovered by German Biologist Walther Flemming, while meiosis was discovered by German Zoologist Oscar Hertwig.
Function
While mitosis helps in the development of organisms, repairing of cells, and healing, meiosis helps in the formation of gametes.
Type of Cells
Mitosis involves somatic cells, whereas meiosis involves germ/reproductive cells.
Number of Divisions
There are two divisions in mitosis, but there is only one division in meiosis.
Number of Daughter Cells
Mitosis produces two daughter cells, while meiosis produces four daughter cells.
Ploidy Level
Mitosis’s ploidy level is diploid, whereas eiosis’s ploidy level is haploid.
Genetic Composition
The genetic composition of mitosis is identical to the mother cell, while the genetic composition of meiosis is different from the mother cell.
DNA Replication
DNA replication in mitosis occurs in interphase, whereas DNA replication in meiosis occurs in interphase 1.
Stages of Prophase
In mitosis, prophase has no phases. However, in meiosis, prophase is divided into 5 sub-stages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.
Pairing of Homologous Chromosomes
In mitosis, homologous chromosomes do not pair, while in meiosis, homologous chromosomes pair.
Crossing Over
In mitosis, there is no crossover, whereas in meiosis, crossing over between homologous chromosomes can be seen.
Chromosome Arrangement in Metaphase Plate
In mitosis, chromosomes are arranged singly on the metaphase plate, while in meiosis, homologous chromosomes are arranged in two parallel lines beside the metaphase plate.
Centromere Division
In mitosis, centromere division occurs in anaphase, while in meiosis, there is no centromere division in anaphase I. However, centromeres divide in anaphase II.
Cytokinesis
Cytokinesis follows every mitosis, but in meiosis, cytokinesis usually occurs after telophase II.
Conclusion
Mitosis is a cell division method that produces two daughter cells that have an equal number of chromosomes to the mother cell and are identical to the mother cell. Meiosis is a cell division method that produces four daughter cells that have half the number of chromosomes from the mother cell and are genetically different from the mother cell. The main difference between mitosis and meiosis is that at the end of mitosis, the chromosome number in daughter cells is equal to the number in the original cell (mother cell), whereas, in meiosis, daughter cells receive half the number of chromosomes from the mother cell.
Reference:
1. Pierce, B.A. (2012), Chromosomes and Cellular Reproduction (4th edition), Genetics A Conceptual Approach
Image Courtesy:
1. “Mitosis schematic diagram-en” by Schemazeichnung_Mitose.svg: Jpablo cadtranslation: Matt (talk) Diagrama_Mitosis.svg: juliana osorio derivative work: M3.dahl (talk) –(CC BY-SA 3.0) via Commons Wikimedia
2. “Meiosis diagram” by Marek Kultys – Own work.(CC BY-SA 3.0) via Commons Wikimedia
