Cytoplasmic determinants are special molecules which play a very important role during oocyte maturation, in the female's ovary. During this period of time, some regions of the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

accumulate some of these cytoplasmic determinants, whose distribution is thus very heterogenic. They play a major role in the development of the embryo's organs. Each type of cell is determined by a particular determinant or group of determinants. Thus, all the organs of the future embryo are distributed and operating well thanks to the right position of the cytoplasmic determinants. The action of the determinants on the

blastomere In biology, a blastomere is a type of cell produced by cell division (cleavage) of the zygote after fertilization; blastomeres are an essential part of blastula formation, and blastocyst formation in mammals. Human blastomere characteristics In ...

s is one of the most important ones. During the segmentation, cytoplasmic determinants are distributed among the

s, at different times depending on the species and on the type of determinant. Therefore, the daughter cells resulting from the first divisions are totipotent : they can, independently, lead to a complete individual. That is not possible after the cytoplasmic determinants have been distributed in the differentiated blastomeres.

Mosaic development

During the mosaic development, the future embryo contains all the distinct cytoplasmic determinants that are distributed in distinct cells. Regions of the organism differentiate very quickly if each cell contains specific cytoplasmic determinants since the first divisions : then the cell divides to give all the other cell of its type, and the same process happens in all types of cells in the organism. As a result, in the case of the mosaic development, cell totipotence disappears very quickly during segmentation. Indeed, each new created cell determines a new region of the future organism, and it is independent from the other ones : thus development is independent from interaction between cells. It is most of all known in certain animals as nematodes ''

C. elegans ''Caenorhabditis elegans'' () is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek ''caeno-'' (recent), ''rhabditis'' (r ...

'', or

ascidians Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" ...

(marine animals).

Regulation development

Other animals show regulation development; their cells show totipotence for a longer time. In these animals, cytoplasmic determinants are more rapidly distributed between newly created cells.

Mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

are an example of animals that undergo regulation development.

Presumptive territories map

The

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

already contains the future organization of the embryo, through cytoplasmic determinants distribution. Presumptive Territories Maps could be established simply by coloring particular regions of the zygote's

References

{{reflist Biology website, embryogenesis part : http://www.botanic06.com/site/EvolVie/physio/embryo5.htm Cell biology