Germ cell (germ cell), also known as gametes (gamete), is multicellular organisms
Which can reproduce cells from primordial germ cells, until finally has differentiated germ cells (sperm and eggs), are haploid cells, which contains a sex chromosome. The term by A - and K - Plante Engler, proposed in 1897 to distinguish with somatic cells. Somatic cells will eventually die, only to have the survival of germ cell generation opportunities. The species mainly rely on germ cells and continue and multiply. The long-term natural selection structure for each species are the best conditions for the survival of the germ cells.
germ cell classification germ cell
Can be divided into Spore
germ cell Spore
It is not for germ cells, usually by asexual. Meiosis
Produce, Sporozoa and plants in protozoa in the.
germ cell gamete
It should be the synthesis of coordination development before zygotic reproductive cells, called cells, by meiosis or mitosis to produce. Gamete producing cells called gamont. This is the primordial germ cells in undifferentiated, male or female gonad differentiation respectively sperm
And eggs. In lower plants, gametocytes directly called in most cases Gametangial
The organ. For example, in Thallophyte
(Thallophyte) isogamous capsule produced isogamous anisogamous capsule produce; Anisogamous
germ cell biological characteristics
germ cell differentiation
Primordial germ cells produce schematic
The signs of differentiation of germ cells in single cell populations. as Volvox
Department of pleodorina has 4 smaller cells lose the ability to divide, to exercise and nutrition metabolism, known as the individual, the other 28 have the ability to divide, known as reproductive individuals; in most small Volvox vegetative cells appeared between a few large germ cells. Polar matter
The rich. Ribonucleic acid
(RNA) the extremely small particles called particles. After fertilization, cleavage
That contains a very granular cells called the polar cell, is the Drosophila primordial germ cells. If the original at the rear of the pole mass injected into an egg in the front, can make the reservation for the development of somatic cells into germ cells.
Germ cell categories
In the side of Ascaris eggs can be seen in a similar situation. There is evidence that amphibian reproductive cells may also be determined in the same way. But I don't know in mammals embryo
And what factors determine some cells into germ cell development. Only know that the germ cells are determined, through the site and migrate to gonad differentiation in there.
germ cell produce
Xu Naideng and Schwann cells still is a major structural component, but in nineteenth Century the work of other scholars have emphasized in cell physiology
Insect germ cells
The function, especially the development and nutrition function. With the cell and its components (especially the nucleus) understanding deepening, the concept of "cell theory" meaning has changed gradually. Xu Naideng's theory of directly promoting the distinction between animal and plant cells are very active in the research work. 1852 Remak (1815 - 1865) points out that the frogspawn is cells in the developing frog embryo in new cells are generated by the existing cell division. He emphatically refuted the free cell formation theory. At this point he got well, (1855) support, which pointed out that the animal and human tissue in many normal and pathological point of view, each cell is from existing cell division and. He asserted: "as a general rule, any kind of development are not starting from scratch, and (must) deny (NATURAL) theory, whether in the development history of the individual parts or in the whole history of the development of biological" (Virchow, 1858:54). Kolliker and some other botanists have come to the same conclusion, at the same time, however, due to Xu Naideng's authority and delay this conclusion is generally accepted in botany. In 1868 Darwin (II:370) is not sure whether the possible free cell formation. Well, later saying "(originally from the cell (omnis) cells, cellula e cellula) although finally was accepted by everyone, but that time on cell (especially nuclear) split the details of the process is not clear (see below," mitosis ").
Because of this cell a new interpretation, to reconsider the fertilization process is ripe. If all parts of the body are composed of cells, then the gonads (ovaries and testes) whether this is true? Male and female "seed material" of what is it? It is made up of cells? Male and female sex cell, what is the difference? This class has been designed with the problem of course was not put out, but these problems must be the logical result of cell theory. Later, more and more obvious until the elucidation of the cellular role in the process of fertilization, the real vitality of the genetic theory can be established. It is in this for decades before the concept of talent shows itself in germ cells.
germ cell Combination Sperm capacitation
Half of sperm with Y chromosomes (23, Y), half with X chromosome (23, X). Ejaculated sperm has athletic ability, but not through the egg zona radiata and surrounding the ability. This is because the sperm head looks a top layer can prevent the enzyme release of glycoprotein. The sperm in the uterus and fallopian tube in the operation process, the glycoprotein degradation by enzyme secretion in the female genital duct, so as to obtain the fertilization ability of this phenomenon called capacitation (capacitation). Sperm in the female reproductive tract of the fertilization ability in general can be maintained for 1 days. The mature egg
The egg is released from the ovary in the middle of second meiosis, and with fallopian tube fluid flow into the fallopian tube, to complete the second meiosis during fertilization. If not fertilized, from 12 to 24 hours after ovulation degradation. Be fertilized
The essence of animal and plant fertilization is the male and female germ cells (gametes) fusion of two gametes, this new zygote respectively to make the same contribution in the formation, and the key process is the nucleus fusion of two gametes, these points to around 1844 has been gradually established and accepted by scholars. The attention of the people began to transfer to the nucleus. The nucleus is not like epigenetic theorists have suggested that only a lump of embryo like substance, amorphous maybe just in fusion only to stimulate the development of the egg? Or is the nucleus is small, but has a tight structure, whether it is not visible to the naked eye microstructure fertilization key role after everything is very precise and specific development process? If the nucleus just as cell growth and cell division of initiater, will think of it in the completion of this task will be dissolved before the new cell division or at least in the formation of gametes before re forming. Since the second half of nineteenth Century the cytologist accepted are physiologist or embryologist training, they are the focus of development, and have no care about continuity of the nucleus. They rarely had to how traits are passed from parents to offspring genetic problems. implantation
The process of embryo implantation gradually buried in the endometrium known (implantation) (imbed), also known as implantation. Implantation is a mammal specific reproductive activity. With starting about fifth - 6 days after fertilization, eleventh - 12 days. Research shows that the embryo
The global receptor protein laminin and endometrium to blastocyst adhesion in endometrium, blastocyst and endometrial microvillus formation randomly staggered formation phenomenon, desmosomes and other special fixing structure of trophoblast cells and endometrial epithelial cells. When implanted, cells in the side of the first contact with the group of trophoblast endometrium, endometrial tissue and secretion of protease digestion and contact the palace, along the digestive tissue by blastocyst endometrial function gap gradually buried layer (Figure). After implantation, the original floating blastocyst is closely attached to the uterine wall, and then buried in the uterus, so as to achieve maternal nutrition and protection, the establishment of the structure of the relationship between mother and child.
The blastocyst implantation site is usually in the uterine body and bottom wall than the front wall. In endocrine disorders, fallopian tube inflammation, adhesion, stenosis and other factors, makes the failed to enter the uterus and implanted outside the uterus, the incidence of ectopic pregnancy (ectopic pregnancy), often occur in the fallopian tube, I also found in the surface of the ovary, uterine broad ligament, mesenteric etc..
germ cell Research progress
In December 24, 2014, the British research group from the University of Cambridge and other colleges and universities in the United States online edition of the peer-reviewed journal Science published an article that from the "master cells" in the stable production of primordial germ cells in experimental success. The research team from the fertilized egg develops into ES cells (embryonic stem cells) and induced by somatic cells into IPS cells (induced pluripotent stem cells) used as a universal cell, and succeeded in the development of primordial germ cells (sperm and eggs of the predecessor). Although so far has been successfully made a case, but through this study, experts found the first important role called "genetic factor SOX17", and the primordial germ cells of stable production becomes a reality.