Larry Oliver
2 December 2016
EXSC 223
Assignment Four
1. Define Meiosis. Compare and contrast meiosis with mitosis.
Meiosis is the nuclear division process that reduces the chromosomal number by half and results in the formation of four haploid (n) cells; occurs only in certain reproductive organs. Mitosis has only one division consisting of prophase, metaphase, anaphase, and telophase, meiosis has two divisions each of the 4 phases listed. Also, meiosis has a synapsis of homologous chromosomes while mitosis does not. During daughter cell number and genetic composition, mitosis has two, each diploid cell is identical to the mother cell. While during meiosis this changes to 4 and each haploid cell contains half as many chromosomes as the mother cell and is inherently genetically different than the mother cell. Another difference is how the chromosomes align at the metaphase plate, during mitosis the chromosomes will align at the center, but during meiosis the tetrads align randomly at the metaphase plate. During meiosis, once telophase I is …show more content…
In the fetal period the oogonia multiply rapidly by mitosis. Then primordial follicles appear as the oogonia change into primary oocytes and get surrounded by a single layer of cells called follicle cells. These primary oocytes begin the first meiotic division but stall late in prophase I and fail to complete it. When the female is born, she is presumed to have a lifetime supply of primary oocytes. By puberty only around 400,000 oocytes remain. At puberty, FSH rescues a small number of growing follicles from fate each month, and then a certain one is selected to become a dominant follicle and continue meiosis I, producing two haploid cells that are dissimilar in size. The small cell is called a first polar body, while the large one is a secondary oocyte. The first polar body may continue its development and undergo meiosis II producing two other small polar
2 December 2016
EXSC 223
Assignment Four
1. Define Meiosis. Compare and contrast meiosis with mitosis.
Meiosis is the nuclear division process that reduces the chromosomal number by half and results in the formation of four haploid (n) cells; occurs only in certain reproductive organs. Mitosis has only one division consisting of prophase, metaphase, anaphase, and telophase, meiosis has two divisions each of the 4 phases listed. Also, meiosis has a synapsis of homologous chromosomes while mitosis does not. During daughter cell number and genetic composition, mitosis has two, each diploid cell is identical to the mother cell. While during meiosis this changes to 4 and each haploid cell contains half as many chromosomes as the mother cell and is inherently genetically different than the mother cell. Another difference is how the chromosomes align at the metaphase plate, during mitosis the chromosomes will align at the center, but during meiosis the tetrads align randomly at the metaphase plate. During meiosis, once telophase I is …show more content…
In the fetal period the oogonia multiply rapidly by mitosis. Then primordial follicles appear as the oogonia change into primary oocytes and get surrounded by a single layer of cells called follicle cells. These primary oocytes begin the first meiotic division but stall late in prophase I and fail to complete it. When the female is born, she is presumed to have a lifetime supply of primary oocytes. By puberty only around 400,000 oocytes remain. At puberty, FSH rescues a small number of growing follicles from fate each month, and then a certain one is selected to become a dominant follicle and continue meiosis I, producing two haploid cells that are dissimilar in size. The small cell is called a first polar body, while the large one is a secondary oocyte. The first polar body may continue its development and undergo meiosis II producing two other small polar