Dicer is constructed of three modules: two RNase III domains and a dsRNA-binding domain called the PAZ domain (named for three proteins that contain this domain: Piwi, Argonaute, and Zwille).

TLS Online TPP Program

#Id: 7018

#Unit 5. Developmental Biology

In many cases, signaling factors maintain the stem cell in an uncommitted state.

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#Id: 7019

#Unit 5. Developmental Biology

Once stem cells become positioned farther from the niche, signaling factors cannot reach them, and differentiation commences.

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#Id: 7020

#Unit 5. Developmental Biology

Intracellular regulatory mechanisms include:

Regulation by cytoplasmic determinants

Transcriptional regulation 

Epigenetic regulation

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#Id: 7021

#Unit 5. Developmental Biology

The adult stem cell is housed in and controlled by its own adult stem cell niche, which regulates stem cell self-renewal, survival, and differentiation of those progeny that leave the niche.

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#Id: 7022

#Unit 5. Developmental Biology

Stem cell niches in the testes of male Drosophila illustrate the importance of local signals, cell-to-cell adhesion, and asymmetric cell division.

TLS Online TPP Program

#Id: 7023

#Unit 5. Developmental Biology

The daughter cell attached to the hub is maintained as a stem cell, whereas the cell that is not touching the hub becomes a gonialblast, a committed progenitor cell that will divide to become the precursors of the sperm cells.