Gametogenesis

Question 1

Spermatogenesis refers to the sperm cell development process. Mitosis involves a single step in eukaryotic cell cycle as follows G1>S>G2>M>C. the cell develops during G1 phase (Brevini & Pennarossa, 2013). Chromosomes replication happens in S phase. During mitosis chromosomes compacts, the nuclear cover disappears whilst spindle fibers start to develop from microtubules that are prophase: centromeres of replica   sister chromatids ally besides the spindle equator that is metaphase. Afterwards chromatids separate and shift to opposite poles in anaphase then the mitotic apparatus is destroyed, independent nuclear covers are developed. Then chromosomes uncoil i.e. telophase and the last stage cell division usually occurs as known as cytokinesis.  

Meiosis refers to a special process that involves the development of four gametes carrying half the quantity of chromosomes located in somatic cells. Meiosis is differentiated from mitosis by two crucial steps (Brevini & Pennarossa, 2013). During the meiosis I prophase, chromosomes usually pairs besides their length and contact in discrete parts of synapsis known as chiasmata. Chromatids are able to swap base pairs through crossing-over. Chromosomes segments re-combination permits recurrent creation of genetic variability and offers a mechanism to correct harm within the DNA helix. Secondly, the non-similar sister chromatids never replicates among serial nuclear divisions. Essentially Meiosis II is similar to mitotic (Wassarman, 2013).

Androgen-fastening protein sequesters   testerone in the seminiferous tubule. Meiosis II is usually hormonally-autonomous. Follicle-stimulating hormone engages in spermiogenesis. Estradiol along with DHT is engaged in spermatogenic process. Additionally hormonal impacts on sperms are indirect and are mediated by sertoli cells (Brevini & Pennarossa, 2013).

Question 2

Oogenesis is the creation of female gametes in the ovary. The progression of oogenesis takes place within the ovary’s external most cover. A primary oocyte starts the initial meiotic division, however, stagnates till afterwards in life when it finishes the division in a growing follicle. The result is a secondary oocyte that will wind up meiosis once it is fertilized.  As earlier indicated the cell beginning meiosis is known as a primary oocyte. The process stagnates within prophase I stage. During the time of birth every future egg is usually within the prophase stage (Wassarman, 2013). During adolescence, the hormone known as anterior pituitary causes the creation of several follicles within an ovary. Then this results to the primary oocyte completing the initial meiotic division. The resulting cell is a division of two unequal parts, thus majority of the cellular material along with organelles ends up in one cell known as a secondary oocyte whilst only a single set of chromosomes along with a little cytoplasm quantity goes to the other cell (Brevini & Pennarossa, 2013). Then the second cell is referred to as the polar body but eventually dies. Afterwards, the secondary meiotic stagnation happens at metaphase II. During ovulation this secondary oocyte is usually released and then shifts on the way to the uterus via the oviduct. When a secondary oocyte undergoes fertilization, the cell goes through meiosis II, thus completing meiosis. This results to the production of a polar body which is a second one along with a fertilized egg that contains all the forty-six chromosomes which makes up a human, half of them originating from the sperm (Wassarman, 2013).  

Question 3

Meiosis refers to the cell division involving gametes. These gametes contain half the initial chromosome numbers, thus the parents reproduce forming a zygote therefore the child obtains half the genetic content from each parent  (Mendel,, 2006).  During meiosis, the genetic information is swapped amongst the maternally along with paternally hereditary parts of chromosomes pair in order to generate new genes combinations. The genetic recombination process assists in increasing the genetic unevenness in a species (Mendel,, 2006). Thus, it permits the transmission of limitless genes combinations from the parent to the child.

References

Brevini, T. A., & Pennarossa, G. (2013). Gametogenesis, early embryo development and stem cell derivation. New York, NY: Springer.

Mendel,, G. (2006). Mendelian Genetics. Retrieved from http://www.pearsonhighered.com/samplechapter/0132241277.pdf

Wassarman, P. M. (2013). Gametogenesis. San Diego: Elsevier Science.