Gastrulation

Mark Jones Writing Assignment 3/5/2017 During the early stages of embryo development, a multitude of signals are being released, some of which specify a cell, such as the neural plate, somites, and notochord, to a dorsal fate. In earlier experiments done by Spemann and Mangold in 1924 that if the dorsal lip of the of the early gastrula was transplanted to a more ventral position in the embryo, the embryo would develop a new secondary axis. The study showed that the organizer respecified the original

embryos. Epithelial morphogenesis is a process driven by actin and myosin apical constriction that results in sheets of cells rearranging to form defined structures. The Drosophila Folded-in-gastrulation (Fog) pathway is one of the best developmental signaling pathways in demonstrating this process. During gastrulation, the epithelial cells undergo a range of morphogenetic mechanisms to form the ventral furrow (VF) and the posterior midgut (PMG). This process begins with Dorsal, a maternal factor, activating

in development too closely related species. When scientist speaks of embryonic development they are referring to the period when egg is fertilized to period of birth or hatching. Early embryology consist of fertilization, cleavage formation and gastrulation. This is followed by the embryonic stage where embryonic cells become organs and tissues termed histogenesis and organogenesis. In humans once the egg is fertilized, the zygotes goes through repeated cell division, a process called cleavage as

stained with toluidine blue dye. The toluidine blue dye allows for the chorion to be visible since it is dyed in purple. Figure 2: D. melanogaster Egg in Early Gastrulation. The above figure shows an egg from D. melanogaster with its chorion removed with bleach. With the chorion removed, it was determined this egg is in the early gastrulation stage. Figure 3: Salivary Gland of D. melanogaster. The above figure shows the salivary gland removed from the third instar of D. melanogaster. Figure 4:

For many years the questions has been raised as to why not all children are affected by Foetal Alcohol Syndrome even if the mother was drinking alcohol during her pregnancy. The theory that genetics plays a role in whether a child will have FAS first came about through studying twins. In a sample size 16 sets of twins, which were all exposed to alcohol while in the uterus, out of the 5 sets of identical twins, in each set both children were affected by FAS. Out of the 11 sets of fraternal twins,

detected at the time of gastrulation and later becomes restricted to the dorsal roof plate of the forebrain (Nagai et al., 1997). A hypomorphic mutation of Zic2 results in a failure of roof plate induction, thus causing a mild form of HPE in the mouse (Nagai et al., 2000). However, mutations in the DNA binding and transactivation domains of Zic2 lead to a more severe form of HPE, owing to the defective development of prechordal plate formation at the time of gastrulation (Warr et al., 2008). Recent

the rate of mitotic division has slowed down, the blastomeres undergo dramatic movements wherein they change their positions relative to one another. This series of extensive cell rearrangements is called gastrulation, and the embryo is said to be in the gastrula stage. As a result of gastrulation, the embryo contains three germ layers: the ectoderm, the endoderm, and the mesoderm. 3.

The development of the chick involves fertilization, division and growth of living cells, and segregation of cells into groups of special function (tissues). Once the egg is laid, some embryonic development has happened and then usually stops until proper cell conditions are met for the incubation to resume. At the beginning of the stages, the cells are alike, but as the embryo develops, cells are specialized. After the start of incubation, a thick pointed layer of cells become visible caudal or

with salamander eggs (Robertis 2008). While doing this experiment, Mangold and Spemann called the dorsal blastopore lip in gastrulating frog embryo “the organizer”, the job of the organizer is for initiation which means 1) the organizer imitates gastrulation and also stops signals starting from the ventral side of the blastula from prompting the skin. 2) Separate the host and donor tissues into secondary embryo into an anterior-posterior and dorsal-ventral

body. Due to importance of the heart an understanding of this complex muscle is necessary. Therefore, today I hope to discuss the embryology of the heart. The formation of the heart begins during the third week of development, the embryo undergoes gastrulation in the embryonic plate producing three germ layers (ectoderm, mesoderm and endoderm). Originally the embryonic plate possesses two germ layers (ectoderm & mesoderm) until pregenital heart cells from the ectoderm migrate through the primitive streak