How many viable cells are produced by oogenesis

Meiosis produces haploid cells with half of each pair of chromosomes normally found in diploid cells. The production of sperm is called spermatogenesis and the production of eggs is called oogenesis. Spermatogenesis, illustrated in Figure 1, occurs in the wall of the seminiferous tubules, with stem cells at the periphery of the tube and the spermatozoa at the lumen of the tube.

Immediately under the capsule of the tubule are diploid, undifferentiated cells. These stem cells, called spermatogonia singular: spermatagonium , go through mitosis with one offspring going on to differentiate into a sperm cell and the other giving rise to the next generation of sperm. Figure 1. During spermatogenesis, four sperm result from each primary spermatocyte. Meiosis starts with a cell called a primary spermatocyte. At the end of the first meiotic division, a haploid cell is produced called a secondary spermatocyte.

This cell is haploid and must go through another meiotic cell division. The cell produced at the end of meiosis is called a spermatid and when it reaches the lumen of the tubule and grows a flagellum, it is called a sperm cell.

Four sperm result from each primary spermatocyte that goes through meiosis. Stem cells are deposited during gestation and are present at birth through the beginning of adolescence, but in an inactive state. Victoria K. Problem 35 Hard Difficulty How many viable cells are produced by oogenesis? Answer C View Answer. Discussion You must be signed in to discuss. Top Biology Educators Emily T.

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This brief prophase II stage [isEmbeddedIn] is followed by metaphase II, during which the chromosomes migrate toward the metaphase plate. During anaphase II, the spindle fibers again pull the chromosomes apart to opposite poles of the cell; however, this time it is the sister chromatids that are being split apart, instead of the pairs of homologous chromosomes as in the first meiotic step.

A second round of telophase this time called telophase II and cytokinesis splits each daughter cell further into two new cells. Each of these cells has 23 single-stranded chromosomes, making each cell haploid possessing 1N chromosomes. As mentioned, sperm and egg cells follow roughly the same pattern during meiosis , albeit a number of important differences.

Spermatogenesis follows the pattern of meiosis more closely than oogenesis, primarily because once it begins human males start producing sperm at the onset of puberty in their early teens , it is a continuous process that produces four gametes per spermatocyte the male germ cell that enters meiosis.

Excluding mutation and mistakes, these sperm are identical except for their individual, unique genetic load. They each contain the same amount of cytoplasm and are propelled by whip-like flagella. In females, oogenesis and meiosis begin while the individual is still in the womb. The primary oocytes, analogous to the spermatocyte in the male, undergo meiosis I up to diplonema in the womb , and then their progress is arrested.

Once the female reaches puberty, small clutches of these arrested oocytes will proceed up to metaphase II and await fertilization so that they may complete the entire meiotic process; however, one oocyte will only produce one egg instead of four like the sperm. This can be explained by the placement of the metaphase plate in the dividing female germ cell. Instead of lying across the middle of the cell like in spermatogenesis, the metaphase plate is tucked in the margin of the dividing cell, although equal distribution of the genetic material still occurs.

This results in a grossly unequal distribution of the cytoplasm and associated organelles once the cell undergoes cytokinesis. This first division produces a large cell and a small cell. The large cell, the secondary oocyte , contains the vast majority of the cytoplasm of the parent cell, and holds half of the genetic material of that cell as well.

The small cell, called the first polar body, contains almost no cytoplasm, but still sequesters the other half of the genetic material. This process repeats in meiosis II, giving rise to the egg and to an additional polar body. These differences in meiosis reflect the roles of each of the sex cells. Sperm must be agile and highly motile in order to have the opportunity to fertilize the egg—and this is their sole purpose.

For this reason, they hardly carry any cellular organelles excluding packs of mitochondria which fuel their rapid motion , mostly just DNA. For this reason, only a single, well-fortified egg is produced by each round of meiosis. Meiosis is a process that is conserved, in one form or another, across all sexually-reproducing organisms.

This means that the process appears to drive reproductive abilities in a variety of organisms and points to the common evolutionary pathway for those organisms that reproduce sexually. It is vitally important for the maintenance of genetic integrity and enhancement of diversity.

Since humans are diploid 2N organisms, failure to halve the ploidy before fertilization can have disastrous effects. For this reason, only very select types of abnormal ploidy survive and do so with noticeable defects ; most combinations containing abnormal ploidy never make it into the world.

The correct reduction of the number of chromosomes insures that once fertilization takes place, the correct amount of genetic material is established in the fertilized egg and, eventually, in the person resulting from it.