Development of egg cells

65913 views

This video show the development of egg cells. In animals, one can usually distinguish 4 stages of embryonic development. 1.Cleavage 2.Patterning 3.Differentiation 4.Grow ClEAVAGE Mitosis and cytokinesis of the zygote, an unusually large cell, produces an increasing number of smaller cells, each with an exact copy of the genome present in the zygote. However, the genes of the zygote are not expressed at first. The activities of cleavage are controlled by the mother\'s genome; that is, by mRNAs and proteins she deposited in the unfertilized egg. Cleavage ends with the formation of a blastula. PATTERNING During this phase, the cells produced by cleavage organize themselves in layers and masses, a process called gastrulation. The pattern of the future animal appears: front and rear (the anterior-posterior axis) back side and belly side (its dorsal-ventral axis)left and right sides. There is little visible differentiation of the cells in the various layers, but probes for cell-specific proteins reveal that different groups of cells have already started on specific paths of future development. Ref: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/EmbryonicDevelopment.html