Homework for chapter 11-Early Development of Amphibian and Fish 1. Following cle
ID: 211868 • Letter: H
Question
Homework for chapter 11-Early Development of Amphibian and Fish 1. Following cleavage in amphibian embryo, there is a mid-blastula transition that prepares the blastula for gastrulation. During this transition, what major events occur? 2. The cells migrate to form three germ layers during gastrulation. What are the key types of cell movements that establish the three germ layers in a gastrula? 3. What are the two signals that construct the organizer? The cells of the organizer ultimately contribute to the four cell types. What are the four cells types? What are the tissues that each cell type can induce? 4. What are the functions of the organizer? 0 fg 9 144 ho f8 f6Explanation / Answer
1. The midblastula transition (MBT) leads to a number of exciting changes that transpire at the midblastula stage in some embryos. The MBT start when the nuclear or cytoplasmic ratio reaches a threshold. when the cytoplasm is divided into more cells, the ratio increases. Before the midblastula transition, All embryonic cells experience cell division at the same time. Only maternal mRNAs are translated.
MBT Events
2 types of cell movement:
Invagination: a sheet of cells called as an epithelial sheet bends inward.
Intercalation: rows of cells move between one another, creating an array of cells that is longer (in one or more dimensions) but thinner.
Ingression: individual cells move from an epithelial sheet and become easily migrating mesenchyme cells.
Involution: an epithelial sheet rolls inward to create an underlying layer.
Convergent Extension: rows of cells intercalate, but the intercalation is highly directional
Epiboly: a sheet of cells spreads by thinning.
3 Protein synthesis which is done by the organizer cells needs the transcription of the relevant genes. Expression of organizer genes depends on Wnt transcription factors. Their messenger RNAs were deposited by the mother in the vegetal pole of the egg. After fertilization and formation of the grey crescent,
the collection on the dorsal side of the embryo shows the activity of Nodal — a part of the Transforming Growth Factor-beta (TGF-) family. Nodal forces the dorsal cells to start the expression of the proteins of Spemann's organizer.
four cell types—pharyngeal endoderm, head mesoderm (prechordal plate), dorsal mesoderm (primarily the notochord), and the dorsal blastopore lip
The pharyngeal endoderm and head mesoderm commence the migration of the organizer tissue and seem to induce the forebrain and midbrain. The dorsal mesoderm provokes the hindbrain and trunk. The dorsal blastopore lip develops the dorsal mesoderm and becomes the chorda neural hinge that produces the tip of the tail.
4 the organizer tissue can be divided into five major functions:
1.The capacity to become dorsal mesoderm
2.The ability to change surrounding mesoderm into lateral mesoderm
3.The strength to dorsalize the ectoderm into neural ectoderm
4The ability to start the movements of gastrulation
5.the ability to cause the neural plate to become the neural tube
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.