Dollo’s law:  A biological generalization positing that complex characters, once lost in evolution, are extremely unlikely to reappear and thus the loss of complex characters is virtually always irreversible.

TLS Online TPP Program

#Id: 6661

#Unit 3. Fundamental Processes

The site of cleavage/polyadenylation in most pre-mRNAs is flanked by two cis-acting signals:  An upstream AAUAAA motif, which is usually located 11 to 30 nucleotides from the site, and  A downstream U-rich or GU-rich element. 

he AAUAAA is needed for cleavage and polyadenylation because deletion or mutation of the AAUAAA hexamer prevents generation of the polyadenylated 3’ end

TLS Online TPP Program

#Id: 537

#Unit 2. Cellular Organization

The shape of a bacterium is governed by its rigid cell wall.

TLS Online TPP Program

#Id: 9632

#Unit 4. Cell Communication and Cell Signaling

Ras has an intrinsically slower rate of GTP hydrolysis, so Ras∙GTP requires the assistance of another protein, GAP.

TLS Online TPP Program

#Id: 5847

#Unit 10. Ecological Principles

Ecosystem replacement - replaces the original community with a different one

TLS Online TPP Program

#Id: 10472

#Unit 4. Cell Communication and Cell Signaling