TLS Online TPP Program

#Question id: 7102


How is the Spemann organizer distinguished from the other mesodermal cells during induction by the cells of the vegetal region?

#Unit 5. Developmental Biology
  1. The cells of the Spemann organizer become different as they pass over the dorsal lip of the blastopore during gastrulation.
  2. Beta-catenin, which has become localized to the nucleus in the Nieuwkoop center as a result of cortical rotation, turns on high levels of the TGF- signalling molecule, Nodal, and this relatively high level distinguishes the adjacent cells of the Spemann organizer from the rest of the mesoderm.
  3. The Spemann organizer is formed from cells of the Nieuwkoop center, which have migrated upward in the embryo.
  4. BMP-4 signalling from ventral mesodermal cells toward the dorsal region specify the dorsal-most cells as organizer.
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TLS Online TPP Program

#Question id: 2423

#Unit 2. Cellular Organization

What is the function of thymosin beta-4?

TLS Online TPP Program

#Question id: 2424

#Unit 2. Cellular Organization

Which of the following statements correctly describe(s) actin?

a. Actin is a highly conserved protein.

b. Multiple actin genes may be found in higher eukaryotes.

c. Actin is the most abundant protein in a eukaryotic cell.

d. Individual actin filaments can be observed by electron microscopy.

e. One end of an actin filament is different from the other. 

TLS Online TPP Program

#Question id: 2425

#Unit 2. Cellular Organization

Which of the following is (are) actin-based structures?

a. adherins belt                        b. contractile ring        c. mitotic spindle

d. nuclear lamina         e. stress fibers

TLS Online TPP Program

#Question id: 2426

#Unit 2. Cellular Organization

Actin assembly in vitro

a. consists of three phases.     

b. requires addition of actin oligomers termed nuclei.

c. requires ATP hydrolysis.

d. is reversible.

e. requires actin-binding proteins.

TLS Online TPP Program

#Question id: 2427

#Unit 2. Cellular Organization

Known functions of actin-binding proteins include

a. severing of long filaments to generate shorter filaments.

b. inhibition of filament polymerization.                   

c. bundling of filaments.

d. acceleration of filament polymerization rates.

e. capping of the (+) end.

TLS Online TPP Program

#Question id: 2428

#Unit 2. Cellular Organization

Which of the following prevent(s) acting disassembly?

a. cytochalasin D         b. jasplakinolide          c. latrunculin               d. phalloidin