Question

A. All roles of beta-catenin.

B. What are the importance of asymmetric cell division in nematode and

lophotrochozoan blastula

C. What are the cascade of gene classes that pattern the anterior-posterior

axis of drosophila.

D. What are the role of chordamesoderm in patterning the axes of frog and

fish embryos.

Answer 1

A.

1. Beta catenin is a part of protein complex that forms the adherens junctions which are necessary for the creation and maintenance of epithelial cell layers and barriers.
2. Beta catenin can also regulate cell growth and differentiation.
3. It may also be responsible for inhibiting the signal between cells which stops cell division and proliferation.
4. It is regulates physiological regeneration process.
5. It also controls the development of embryo.

B.

Asymmetric partitioning is one of the  major events  necessary for developmental processes. After spermatogenesis, sperm are streamlined by discarding unnecessary cellular components into cellular discards called residual bodies (RBs). In nematode spermatogenesis, the asymmetric partitioning occurs briefly after anaphase II, and both microtubules and actin partition into a central RB. Intact microtubules reorganize and move to non-centrosomal sites at the RB-sperm boundary whereas actin through cortical ring expansion and clearance  from the poles reorganizes. Consequently, partitioning yields one functional sperm with the X-bearing chromosome complement and an RB with the other chromosome set.

C.

• The antero-posterior axis patterning in Drosophila involves mainly 3 genes ; maternal effect genes, segmentation genes, and homeotic genes.
• The polarity of the egg and embryo is defined by the maternal effect gene via localization of mRNA.
• The crucial maternal effect genes which patterns the anterior regions, comprising the head and thorax of the embryo are Bicoid and hunchback.
• Nanos and Caudal genes dictates the posterior abdominal segments.
• The mRNA molecules get localized to specific region based on the attachment to the microtubules.The Bicoid mRNA thus attach to the anterior end of the oocyte.
• The Hunchback and Caudal mRNA are distributed evenly all throughout the egg.
• The gap genes (a part of the segmentation genes) establish the segmented body plan of the embryo along the anterior-posterior axis. These genes code for 14 para segments that relate to the final anatomical segments.
• The gap genes, which are a part of the segmentation genes that establish the segmented body plan of the embryo along the anterior-posterior axis. These genes code for 14 para segments that relate to the final anatomical segments.

D.

• Chroma mesoderm also called as "Axial mesoderm" is a type of mesoderm that lies under the neural tube along the central axis and give rise to notochord.
• It induces the formation of neural plate.
• It plays important role in forming the notochord as well as in inducing development of the overlying ectoderm into the neural tube.
• It also induce the formation of vertebral bodies.