Timing and Principle Characteristics of Developing Female and Male Germ Cells From Differentiation in Early Embryo to Point of Fertilization
Principle Characteristics Male and Female Germ Cells
The female and male germ cells are reproductive cells that fuse with one another during fertilization (Encarta, 2005; Burfoot, 1999). Each possesses unique characteristics and molecular structure during the prefertilization phase of development and post fertilization. These characteristics are influenced by the production of various hormones in the male and female body.
Fertilization occurs when the materials from two gametes come together to form an embryo. The female gamete is often referred to as the egg or female germ cell whereas the male gamete is often referred to as sperm or the male germ cells (Encarta, 2005; Burfoot, 1999). Developing female germ cells are generally large and contain nutrient reserves including what is referred to as the egg 'yolk' or sometimes white and typically are immobile (Encarta, 2005; Burfoot, 1999).
Male germ cells are highly mobile if normal and generally contain little nutritional recourses; most are very tiny and contain substances called centrosomes (Burfoot, 1999). Male and female germ cells both contain a set of chromosomes and hence are referred to as haploid (Encarta, 2005). After fertilization occurs a zygote results containing two sets of chromosomes now called the diploid (Encarta, 2005).
Successful fertilization can only occur when the male and female germ cells both are at proper stages of fertilization. Mature male cells are thus capable of penetrating female germ cells or the egg. After fertilization the female germ cell supplies cytoplasm and nutrients to nourish the embryo while the male sperm or germ cells provides more functional centrosome to encourage mitosis or cell division (Encarta, 2005).
Prior to fertilization germ cells reside in the seminiferous tubules at varying levels of maturation and exist alongside sertoli cells or...
These cells are linked by tight junctions to male germ cells resting along the "basement membrane of the seminiferous tubules" (IVF, 2005:1). Male germ cells are isolated prior to spermatogenesis to maintain them immunologically, and are thought to be nourished by sertoli cells; most germ cells are arranged "in an orderly manner from the basement membrane to the lumen" (IVF, 2005:1). There is little other molecular information available regarding male germ cells despite their "critical position in mammalian physiology" except that they contain genetic information that is carried and combined with the fertilized egg (Orwig, et. al, 2002: 11706).
Once fertilization of a mature female gamete occurs meaning a female germ cell has participated in the fertilization process and is now in the process of creating a new organism, the new mature egg is often also referred to as a germ cell or oocyte (Gribbin, 2001). The zygote is the new organism consisting of combined chromosomes resulting from the fusion of the male and female mature gametes that occurs after fertilization (Gribbin, 2001).
The female germ cell alters significantly once the sperm enters or fertilizes the egg facilitating the transformation from egg to zygote and subsequent embryo. The fertilized egg is "surrounded by the fertilization membrane" which activates the egg and a gelatinous film appears after some time (Loeb, 1913). Nuclear material then forms which facilitates cell division causing the egg to elongate and segment (Loeb, 1913).
Male Female Timing Reproduction
When it comes to reproduction and fertilization of female germ cells timing is everything. A female germ cell may become mature but not be fertilized in time by a mature male germ cell resulting in an embryo. Likewise mature male germ cells may be readily available for fertilization but the female germ cell may not have descended or be fit for fertilization. Even under optimal circumstances and conditions…
