Mitosis vs Meiosis: Introduction
Both are type of cell division taking place in every eukaryote. But the main difference is Mitosis produces Diploid Somatic cells identical to parent and Meiosis give rise to cells which forms a new progeny which are genetically different from the parent by producing haploid gametes.
The differences vary mitosis from meiosis producing regular somatic cell and differentiated gametes of future progeny respectively.
Out of 2 cellular divisions in meiosis; Meiosis II is more similar to mitosis with the difference in the end products of haploid gametes and regular diploid somatic cells respectively.
Mitosis vs Meiosis
|Two daughter cells are produced from a single cell||Four daughter cells are produced from a single cell|
|Chromosomal segregation separates equal number of chromosomes to the progeny||Chromosomal segregation separates only half chromosomes of the single cell|
|Infinite cell cycle rotation varies in different cells||Single rotational cell cycle|
|A cell cycle involves 2 Gap phases and one synthesis and Mitotic phase||Cell cycle involves 2 continuous Meiosis preceded by single gap phase and synthesis phase|
|No homologous chromosomes are found||Homologous chromosomes are attached during Prophase|
|Recombination is not required as the division involves a replication of unmodified genetic material||Recombination is the main specialty of meiosis where the genetic material is non – sister chromatids are exchanged with each other|
|Daughter cells are identical to parent||Daughter cells are varied from the parent|
|During development the division produces number of differentiated cell lineage based on the location, hormone regulation etc.,||During division it produces single lineage of cells|
|Chromosome divides during Anaphase||Chromosomal division is during Anaphase II|
|The cells can be Haploid or Diploid||The cells undergoing such division contains only diploid number of chromosomes and above|
|Cells which undergo such division are called as Somatic cells||Such division gives rise to sex cells called Gametes|
Mitosis vs Meiosis Diagram
I. Mitosis Diagram
II. Meiosis in Oocyte
III. Meiosis in Sperm
Why We Need Meiosis?
o Eukaryotes are evolved and well distinguished for the various adaptive features to survive the dynamic changes and evolved along the changes.
o Changes in the environment was followed by the adaptation in organism for the respective environment was motivated by an act of survival and to ensure a progeny to develop the lineage thereby sustaining life on earth.
o Environmental modification led changes in animals and plants; regulated the diversification and population growth of all organism by frequent modifications in niche where the organism functions to its fullest; challenging the organisms to promote change in functionalities for the survival factor.
o Charles Darwin pointed out the Theory of “Natural Selection” where the organisms are naturally and randomly selected by nature to develop lineage.
o He called it the ” Survival of Fittest” where the organisms suitable for the environment survived and others which couldn’t survive became extinct.
o The Survivors became the key organism for the variability among the genus, species level which on further adaptions evolved to give rise to new classes and phyla.
o Changes governing evolution are inherited from parent to offspring; is sexually selected – another phenomenon of evolution and diversification; mediated by special type of cell division Meiosis.
o Gametes of meiosis inherits the changes from parent during fertilization to produce competitive offspring for better survival and variability from parents by giving it a unique identification and distinction from the parent.
o Differentiation, compatibility to the environment is genetically marked and inscribed in the genes from parents separately before the fertilization.
o The inheritance of the qualities is determined post fertilization in zygote involves principles of genetics while exhibiting features of an organism.
o Such unique, distinctive characteristics of an organism predetermined in gametes of parents; formed by a reductive division.
o Meiosis revolves around the components of cell cycle and molecular activation by an organism.
o The cell of meiosis initially are a result of mitosis and meiosis is the smallest but significant part in life history of any organism.
o The specialized division becomes more significant for its role in determining the characteristics of future progeny and aids in variability which on long run evolves the organism.
o Meiotic steps are crucial in determining half feature of an organism by each parent to make up the whole organism.
Significance of Meiosis
1. Evolution of sexual reproduction in eukaryotes are marked by Meiosis. Sexual reproduction becomes and important characteristic feature of meiotic division; involves maternal gametes and paternal gametes to determine the ability of an organism.
Sexual reproduction involves fertilization between same species with distinct genetic characters originated from their unrelated immediate ancestors to produce viable gametes to compete and accustomate to the environmental challenges for survival.
2. Meiosis is conserved in broader terms among all sexually reproducing eukaryotes. Broadly, the mechanism of meiosis is similar in all eukaryotes involving same steps and function.
Changes from the preset is that each organism takes different time to proceed the cycle of meiosis and end products can be different from each species in structure and function.
3. Meiosis maintains a constant chromosome number. Advantage of using meiosis over mitosis for gamete production is to maintain the chromosome number.
On mitotic division; the chromosomes produce daughter cells with diploid chromosome number; if the same prevails; for meiosis the chromosomes double on each fertilization resulting in doubling at each generation.
For example: 2n –> 4n –> 8n –> 16n…….. infinity.
4. Recombination of paternal and maternal chromosomes produces genetic variability, diversity and in turn evolution.
Recombination is a process of exchange of genetic material between maternal and paternal chromosomes with the progeny to get a combination of both traits and not either of the traits causing reduced viability in offspring.
Crossing over is a step-in prophase where the homologous chromosomes pairs by a synaptonemal complex and crosses each other in further steps by a chiasma; providing a bridge for the exchange of the genetic material.
5. Recombination takes place with rules and by the process of law of independent assortment. The law stated by Mendel says that the genetic material of maternal or paternal chromosomes are independently crossed over to recombine with each other to produce variabilities in the haploid gametes to express traits of both maternal and paternal in origin.
6. Positive adaptation caused by mutation suitable for the environment is naturally selected and carried over to next generation. Meiosis is the process of random selection and fusion of male and female gametes to future generation.
Any changes in the germ cell chromosomes are inherited to the next generation and are exposed to the environment; surviving with the mutation in ease might take the changes to generations further and undesirable change caused by mutation might be eliminated rapidly because of the in functionality of the process.
7. The segregation, crossing over and recombination of the chromosomal components ensures the variable inheritance of parental chromosomes. The recombination produces diversity among the population on long run produces variability and then evolve to new organism or to any environment.
8. After the meiosis the post – miotic process or the end product might vary from species to species. Plants after meiosis produces 4 microspores in anthers and 4 megaspores in Female. The microspores 3 degenerates one fuse with one megaspore.
Later, the remaining haploid megaspores combine to form endosperm in one stage to provide a developmental part of other fusion.
Mitosis vs Meiosis Citations
- Recombination, Pairing, and Synapsis of Homologs during Meiosis. Cold Spring Harb Perspect Biol . 2015 May 18;7(6):a016626.
- Meiosis: the chromosomal foundation of reproduction. Biol Reprod . 2018 Jul 1;99(1):112-126.
- Abnormal mitosis in reactive astrocytes. Acta Neuropathol Commun . 2020 Apr 15;8(1):47.
- Mitosis in vertebrates: the G2/M and M/A transitions and their associated checkpoints. Chromosome Res . 2011 Apr;19(3):291-306.