What is Meiosis?
Meiosis is the process that creates gametes, better known as eggs and sperm, which are essential for sexual reproduction. Gametes are formed from germ cells, which are found in the reproductive organs, the testes (males) or the ovaries (females). The germ cells are undifferentiated cells that remain inactive until an organism reaches sexual maturity. When an organism needs to begin reproducing the germ cells become active and undergo meiosis to produce eggs and sperm.
Meiosis is necessary because diploid organism have two sets of chromosomes, one paternal and one maternal. For a diploid organism to undergo sexual reproduction it needs to create gametes that contain only one set of chromosomes so the number of chromosomes in the next generation remains the same (ie one paternal and one maternal). This is also why we don’t look exactly like our parents; we are a genetic mix of our father and mother. To create gametes with only one set of chromosomes, germ cells replicate their DNA making two copies of the maternal and paternal chromosomes and then undergo two rounds of division, which creates four gametes each with one set of chromosomes. When sexual reproduction occurs a gamete from the mother is fertilized by a gamete from the father. Once these two cells are fused the number of chromosomes in that cell is brought back to two sets (one paternal and one maternal).
A key step in meiosis is the exchange of genes between the maternal and paternal chromosomes. During meiosis the two sets of chromosomes are paired with each other and held together by “crossing over” events where genetic material from one set is exchanged with that of the other set. This is the process which helps increase genetic diversity in a population. By exchanging genes between the two sets of chromosomes the next generation of offspring will be genetically different from its parents.
What would happen if meiosis suddenly disappeared?
As explained above meiosis is necessary for sexual reproduction and for increasing genetic diversity. If meiosis were to disappear tomorrow all sexually reproducing organisms would stop having offspring. This means no more babies, puppies, kittens, plants etc. While all the living children and adults of sexually reproducing organisms would continue living there would be no future generations. This would lead to the extinction of the majority of the world’s diploid species.
How would humans survive the loss of sexual reproduction?
However, there are other organisms that do not depend on sexual reproduction and instead are asexual. These organisms are able to essentially clone themselves to create new offspring that are genetically identical to their parents. Currently, scientists are able to clone animals and could theoretically clone humans. However, there are many ethical issues surrounding the cloning of humans, which has prevented cloning up to this point. If the human race were facing extinction we would probably reconsider cloning as an option for survival. It is also possible that we would work to create new ways of cloning that would allow for genetic diversity which would be lost if we became a clonal species.
In addition to the issue of human extinction, our food sources (plants and animals) are also produced by sexual reproduction. To have enough food to sustain the world, clonal versions of plants and animals would have to be created and released into the world to repopulate all the sexual species. In practice this would be almost impossible to accomplish and would have drastic consequences on the environment and the world.
In short, if meiosis disappeared tomorrow the world would become a drastically different place and it is likely most species would not survive extinction and those that did would be living in a completely different world.
June 27, 2016
