Hans Speeman - inductive interactions in regulative development
Hans Speeman and Hilde mangold - primary embryonicinduction
They transplanted a group of cells from the dorsal lip of the blastopore (a region known as the "organizer") from an early gastrula embryo of a newt into the ventral side of another newt embryo. The result was the formation of a second, complete embryonic body axis, including a notochord, neural tube, and somites
Dorsal blastopore lip transplantations
Induction of neural ectoderm and dorsal mesoderm: BMP inhibitors
Syncytial cleavage pattern - drosophila
Fish cleavage pattern - discoidal
Chick cleavage pattern - discoidal
Mammal cleavage pattern - rotational
Frog cleavage pattern - radial
Fish yolk descriptor - telolecithal
Chick yolk descriptor - telolecithal
Mammal yolk descriptor - isolecithal
Frog yolk descriptor - telolecithal
Fish cleavage extent - meroblastic
Chick cleavage extent - meroblastic
Mammal cleavage extent - holoblastic
Frog cleavage extent - holoblastic
The first cell division in the frog embryo occurs at the animal pole (animal hemisphere) while the second cell division occurs at the vegetal pole (vegetal hemisphere). This results in an unequal distribution of cytoplasmic components between the two daughter cells.
Telolecithal eggs have one large yolk mass located on one side of the egg, resulting in asymmetrical cleavage patterns.
Cleavage patterns can be classified based on their shape, such as syncytial or radial.
Yolk descriptors refer to the location of the yolk within the egg, with telolecithal eggs having most of the yolk concentrated at one end and isolecithal eggs having evenly distributed yolk throughout the egg.
Isolecithal eggs have evenly distributed yolk throughout the entire egg, leading to symmetrical cleavage patterns.
Meroblastic cleavage involves only part of the zygote undergoing mitosis, leaving some unfertilized ooplasm behind.
Holoblastic cleavage involves all parts of the zygote undergoing mitosis, with no unfertilized ooplasm remaining.
Cleavage refers to the process by which a fertilized ovum divides into smaller cells through mitosis.
Yolk location within the egg can also influence cleavage patterns, with telolecithal eggs having more asymmetry compared to isolecithal eggs.
There are three main types of cleavage: syncytial, discoidal, rotational, radial, and holoblastic.
Syncytial cleavage involves multiple nuclei within a single cytoplasm.
During gastrulation, the blastula undergoes invagination, forming a three-layered structure called the gastrula.