Two to four monomers of DnaAATP bind at the origin, and after release of DiaA, they recruit two “pre-priming” complexes of the DnaB helicase bound to DnaC-ATP, so that there is one DnaB–DnaC-ATP complex for each of the two (bidirectional) replication forks.

TLS Online TPP Program

#Id: 666

#Unit 3. Fundamental Processes

Short repeating sequence from the human telomere forms three stacked G quartets.

TLS Online TPP Program

#Id: 667

#Unit 3. Fundamental Processes

Telomerase, a reverse transcriptase that contains an RNA template, repeatedly adds TTAGGG repeats

TLS Online TPP Program

#Id: 668

#Unit 3. Fundamental Processes

Embryonic cells, germ-line cells, and stem cells produce telomerase, but most human somatic cells produce only a small amount of telomerase as they enter S phase.

TLS Online TPP Program

#Id: 669

#Unit 3. Fundamental Processes

As a result of their modest telomerase activity, their telomeres shorten with each cell cycle.

TLS Online TPP Program

#Id: 670

#Unit 3. Fundamental Processes

Extensive shortening of telomeres is recognized by the cell as a double-strand break and consequently triggers cell cycle arrest and apoptosis.

TLS Online TPP Program

#Id: 671

#Unit 3. Fundamental Processes

In mammals, six telomeric proteins (TRF1, TRF2, Rap1, TIN2, TPP1, and POT1) comprise a complex called shelterin