1) Your laboratory studies the common mechanisms by which gastrulation movements
ID: 50067 • Letter: 1
Question
1) Your laboratory studies the common mechanisms by which gastrulation movements are initiated. For this reason, your laboratory uses both sea urchins and fruit flies as model organisms.
A) Propose one way to disrupt gastrulation in both the sea urchin and the fruit fly embryos using one of the following reagents. Assume that you are adding the reagent after cleavage stage/syncytial blastoderm stage. Explicitly state HOW your chosen reagent disrupts gastrulation. (5 points)
Cytochalasin B- disrupts filamentous actin formation
Nocodazole- disassembles microtubules
Calcium chelator- absorbs calcium in the environment
B) Give one potential reason for why mice were not included among the list of model organisms being used in your studies. (5 points)
Explanation / Answer
Gastrulation can be disrupted by using the reagent Nocodazole, which disassembles microtubules. Disruption of microtubules results in the breakdown of basement membrane and its stablisation results in the retention of basement membrane. Thus, microtubules have significant role during gastrulationItion.
It is proposed that mediolateral cell intercalation is the driving force for morphogenesis process. This intercalation begins in a group of cells called vegetal alignment zone. Vegetal alignment zone is a subpopulation of cells in Spemann's orgaizer and they spread to most of the marginal zone. Disrupting the microtubules with Nocodazole would inhibit the formation of vegetal alignment zone. In such embryos that lack vegetal alignment zone, mediolateral intercalation, involution, and convergent extension of the marginal zone do not occur. Even though the motility of the cell continues, and the anterior notochordal and somitic mesoderm differentiate in the pre-involution marginal zone, the posterior notochordal and somitic mesoderm do not differentiate. This disrupts gastrulation.
However, if Nocodazole is added to midgastrula embryos, after the formation of vegetal alignment zone, it would show no significant affect on gastrulation, as it does not inhibit mediolateral cell intercalation, involution and convergent extension, or differentiation of posterior notochord and somites. Thus, microtubules are essential for orienting and polarizing at stage 101/2 the first cells that undergo mediolateral intercalation and form the vegetal alignment zone. Treating the embryos during this stage with Nocodazole would disrupt their gastrulation.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.