Mitosis is one cell dividing its nucleus and DNA into two cells that have the same amount of DNA as the original cell. Meiosis is one cell dividing into four cells that each has half the amount of DNA that as in the original cell.
The advantage of sexual reproduction is that it generates genetic diversity, which can make a population of organisms better able to survive harsh environmental conditions. Sexual reproduction is possible because of meiosis, which is the shuffling of genes within a cell before it divides into four sperm or eggs. However, mitosis is required in order for a multicellular organism to have the organs that sustain meiosis and sexual reproduction.
In this post, we're going to go over the significance of mitosis and meiosis, some of the differences with mitosis vs meiosis, and how they relate to the cell cycle.
Mitosis vs Meiosis: Meiosis Produces Gametes
Meiosis is what produces an organism's gametes, sperm or eggs that fuse to create a new zygote. Gametes only have half the normal number of chromosomes, or strands of DNA, that a normal cell does. So, two of them must fuse in order to form a new zygote that will develop into a new organism.
In sexually reproducing organisms, gametes are only produced by meiosis, not mitosis. During the cell cycle and the process of meiosis, not only do the gametes go from diploid to haploid (half the DNA in each gamete), but they also have "crossover" events as it occurs called "DNA recombination". This further ensures that each and every gamete produced is unique and varied to produce a genetically diverse next generation.
Mitosis vs Meiosis: Mitosis Builds Reproductive Organs
In order to go from a fertilized embryo to a fully functional multicellular organism, that embryo must undergo rapid and extensive mitosis. This leads to the development of a new organism. The significance of mitosis and meiosis is that meiosis creates the gametes that make reproduction possible while mitosis allows the organism to grow and develop in order to allow for later further reproduction.
For example, reproductive organs that produce gametes via meiosis were built by cells that underwent mitosis and go through the cell cycle. Thus, in these organisms, meiosis is only possible because mitosis made organs that nurture the cells to undergo meiosis.
The Reproductive Endocrine System
The human reproductive system is controlled by the brain. The sperm are produced in the testicles, and the eggs are produced in the ovaries, but both of these organs receive commands from the brain.
They also talk back to the brain in a process called feedback. The brain and the reproductive organs talk to each other by releasing endocrine hormones into the blood. Just as with the reproductive organs, the brain was formed by cells that underwent mitosis. In fact, the cells that produce the hormones in each organ were the result of mitosis, not meiosis.
Thus, the significance of mitosis and meiosis is that one really cannot work without the other when it comes to sexual reproduction and multicellular organisms.
Spermatogonia and Oogonia
Another important factor of mitosis in sustaining meiosis is that the cells that undergo meiosis to produce gametes can also under mitosis. These cells undergo mitosis before so that they can make more copies of themselves. The more copies there are of them, the more gametes can be produced later on.
In men, these cells are called spermatogonia. In women, they are called oogonia (oh-oh-go-knee-uh). Mitosis of spermatogonia is how a man can produce sperm even in old age. It is also how a woman has 400,000 eggs by the time she is born.
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