In the case of the bacterial enzyme bearing s70, this transition, often called isomerization, does not require energy derived from ATP hydrolysis and is instead the result of a spontaneous conformational change in the DNA– enzyme complex to a more energetically favorable form.

TLS Online TPP Program

#Id: 190

#Unit 5. Developmental Biology

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TLS Online TPP Program

#Id: 191

#Unit 5. Developmental Biology

At slightly lower concentrations (intermediate concentrations), activin (about 100 molecules per cell) activated the Xbra gene and instructed the cell to become muscle.

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#Id: 192

#Unit 5. Developmental Biology

At lower concentrations of activin, genes were not activated, and the “default” gene expression instructed the cells to become blood vessels and heart.

TLS Online TPP Program

#Id: 930

#Unit 5. Developmental Biology

Stem cells are sometimes referred to as “undifferentiated” due to this maintenance of proliferative properties.

TLS Online TPP Program

#Id: 931

#Unit 5. Developmental Biology

Stem cell potential refers to the range of cell types a stem cell can produce. 

TLS Online TPP Program

#Id: 932

#Unit 5. Developmental Biology

A totipotent stem cell can generate all cell types of both embryonic and extraembryonic lineages.