Before Life As We know it
Individuals tend to question how life came about and how we ended up as the Homo sapiens that we are male or female respectively. Little do they know there are several processes, which take place before we eventually become the person we are. “It appears to be reasonably established that the functional gametes of many organisms are derived from primordial germ cells already present in early embryogenesis”(Clement 3). Before gametogenesis, the primordial germ cells drift towards the gonads, where eventually they differentiate into gametes. However, gametogenesis is the process leading to gamete production, the development and maturing of sex cells through meiotic division. This is a situation whereby two diploid precursors undergo cell division and differentiation to form mature haploid gametes. There are two forms of gametogenesis, spermatogenesis (male), and oogenesis (female). “Meiosis and gametogenesis are critical processes in the transmission of genetic material to subsequent generations during sexual reproduction”(Frederic 8346). In other words, gametogenesis is the production of sperm and eggs, through the process of meiosis. “During meiosis, two cell divisions separate the paired chromosomes in the nucleus and then separate the chromatids that were made during an earlier stage of the cell’s life cycle, resulting in gametes that each contain half the number of chromosomes as the parent”(Boundless 1).
As stated, there are two forms of gametogenesis, spermatogenesis and oogenesis. Spermatogenesis is the assembling of mature spermatozoa; it is the process whereby male primary germ cells go through division and produce spermatogonia from which spermatocytes are derived. These spermatocytes gradually divide into spermatids, which mature into sperms. “During spermatogenesis, four sperm result from each primary spermatocyte, which divides into two haploid secondary spermatocytes; these cells will go through a second meiotic division to produce four spermatids”(Boundless 1).
http://jp.physoc.org/content/578/1/25/F1.expansion.html Fig.1. The diagram above briefly summarizes the process of spermatogenesis; it shows how the diploid spermatogonium is formed from the primordial germs cells. The primary spermatocytes divide into two secondary spermatocyte that are haploid; this occurs in meiosis 1. Thereafter, the secondary spermatocytes further divide into four early spermatid that are also haploid, theses spermatids eventually become the sperm cells. In humans, the process of spermatogenesis takes approximately 74 days; this includes transport on ductal system. The testes produce 200 to 300 million spermatozoa daily. “In the male spermatogenesis occurs from puberty to old age, producing immense numbers of spermatozoa at an average rate of 1.5 million spermatozoa per minute”(Cuschieri 1).
On the other hand, oogenesis is the creation of mature ova, is the creation of an ovum (egg cell). This is the female form of gametogenesis, which involves the maturation of the diverse stages of the immature ovum. In oogenesis, diploid oogonium undergoes mitosis until eventually one develops into a primary oocyte, which causes the first meiotic division. It completes this division as it matures in the follicle, resulting in haploid secondary oocyte and a smaller polar body. “The process of oogenesis occurs in the ovary’s outermost layer. A primary oocyte begins the first meiotic division, but then arrests until later in life when it will finish this division in a developing follicle. This results in a secondary oocyte, which will complete meiosis if it is fertilized”(Boundless1). http://faculty.southwest.tn.edu/rburkett/A&P2_reproductive_system_lab.htm
Fig.2. Shows the process of oogenesis, the ovarian cell undergoes mitosis to form the primary oocyte, which has 46 chromosomes, after which first...
Cited: Zuckerman, B. “Cytogenetic, Host – Parasite Interactions, and Physiology”.
Frederic, Chalmel. “The Conserved Transcriptome in Human and Rodent Male Gametogenesis”. 104,No.20 (2007): 8346-8351.
Jagiello, David. “Bio regulators of Reproduction” (2012): 122-125.
Clement, Markert. “The Developmental Biology of Reproduction”(2012): 3-6.
“Gametogenesis (Spermatogenesis and Oogenesis)” Boundless. Accessed Monday march 9th 2013.
“Gametogenesis” Wikipedia, accessed Monday march 9th 2013.
Cuschieri Alfred “Gametogenesis” staff.um.edu.mt/acus1/GAMETOGENESIS.html accessed Monday march 9th 2013.
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