ABA signaling in guard cells is largely mediated through the second messenger Ca2+.

TLS Online TPP Program

#Id: 3044

#Unit 3. Fundamental Processes

In mammalian systems (where the DNA polymerase does not have a 5'- 3' exonuclease

activity), Okazaki fragments are connected by a two-step process. Synthesis of an Okazaki fragment displaces the RNA primer of the preceding fragment in the form of a "flap’’.

The base of the flap is cleaved by the enzyme FEN1 (flap endonuclease 1 ) .

TLS Online TPP Program

#Id: 3045

#Unit 3. Fundamental Processes

FEN 1 functions as an endonuclease, but it also has a 5 '-3' exonuclease activity. In DNA repair reactions, FEN 1 may cleave next to a displaced nucleotide and then use its exonuclease activity to remove adjacent material.

TLS Online TPP Program

#Id: 3046

#Unit 3. Fundamental Processes

The general importance of FEN 1 is that it prevents flaps of DNA from generating structures that may cause deletions or duplications in the genome.

TLS Online TPP Program

#Id: 3047

#Unit 3. Fundamental Processes

DNA ligase seals nicks between adjacent nucleotides by employing an enzyme-AMP intermediate.

TLS Online TPP Program

#Id: 3076

#Unit 3. Fundamental Processes

The division of a bacterium into two daughter cells is accomplished by the formation of a septum.

TLS Online TPP Program

#Id: 3077

#Unit 3. Fundamental Processes

Septum, a structure that forms in the center of the cell as an invagination from the surrounding envelope