Question

please explain the fertilization process of the zebra fish, be sure to include the effect that the actual fertilization event has on subsequent cleavage and gastrulation in the model.

Answer 1

The fertilization process of the zebra fish:

Fertilization:

The gametes of male zebra fish are sperm cells with no acrosome whereas female gametes are oocytes together fertilize by entering into the micropyle to from a diploid embryo followed by formation of cytoplasmic cap. This is followed by cleavage of embryonic cells in the from of "meroblastic" to generate poles with yolk.

Mid-Blastula Transition ---> formation of yolk syncytial layer ---> gastrulation as describe below

Gastrulation always initiates with invagination of the embryonic bottle cells followed by involution of mesoderm and finally epiboly of ectoderm.

Gastrulation begins at the vegetal pole in the tunicates followed as this vegetal pole will become future dorsal side component composed of nutrients. Initially, zygotic cells will produce invagination as to produce “endoderm” that produces blastopore. This step is followed by involution of mesoderm that migrates further into the blastopore. Third step is followed by formation of epiboly of ectoderm that covers the embryo finally formation of anterior-posterior axis with neural tube formation. This is going to enable cell migration and cell movement. In the tunicates, notochord supports as a flexible rod of gelatinous for adult form. The similar structural formation during evolutionary development in lancelets has been observed during their embryonic development.

The genes responsible for the generation of “embryonic organizer” are gene “Goosecoid” and the ventral genes Vent1 and Vent2 in case of vertebrate fish models (Zebra fish) for gastrulation. In case of vertebrate mouse models Goosecoid –organizer specific genes are essential for mesodermal patterning at the time of gastrulation.