Each single strand of the b-sheet structure can be pictured as a twofold helix, that is, a helix with two residues per turn.

The arrangement of successive amide planes has a pleated appearance due to the tetrahedral nature of the Ca atom.

TLS Online TPP Program

#Id: 2358

#Unit 5. Developmental Biology

Each pluripotent neoblast generates a colony of neoblast cells in the flatworm.

TLS Online TPP Program

#Id: 2359

#Unit 5. Developmental Biology

First possible mechanisms for neoblast specification during regeneration:

A single pluripotent neoblast is responsible for generating new cell progenitors that form the multipotent cells of the blastema.

TLS Online TPP Program

#Id: 2360

#Unit 5. Developmental Biology

Second possible mechanisms for neoblast specification during regeneration:

Multipotent progenitor cells are positioned throughout the planarian with their lineages specified based on their position. These divide and produce postmitotic blastema cells that differentiate into their specified fates.

 

TLS Online TPP Program

#Id: 2361

#Unit 5. Developmental Biology

The gene smedwi-1 is expressed by all neoblasts and the most common marker for their identification across planarian species.

TLS Online TPP Program

#Id: 2362

#Unit 5. Developmental Biology

Zeta and Sigma neoblasts are morphologically indistinguishable, but they express different gene regulatory networks.

TLS Online TPP Program

#Id: 2363

#Unit 5. Developmental Biology

Sigma neoblasts expresses soxP-2