In the germ line, PAL-1 synthesis is prevented by the PUF-8 protein, which binds to the 3′ UTR of pal-1 mRNA and blocks its translation.

TLS Online TPP Program

#Id: 5921

#Unit 3. Fundamental Processes

Each Okazaki fragment starts with a primer and stops before the next fragment

TLS Online TPP Program

#Id: 5922

#Unit 3. Fundamental Processes

The 5’–3’ exonuclease activity removes the RNA primer while simultaneously replacing it with a DNA sequence extended from the 3’–OH end of the next Okazaki fragment. 

TLS Online TPP Program

#Id: 5923

#Unit 3. Fundamental Processes

To replace the RNA primers with DNA, an enzyme called RNaseH recognizes and removes most of each RNA primer. This enzyme specifically degrades RNA that is base-paired with DNA. RNase H removes all of the RNA primer except the ribonucleotide directly linked to the DNA end.

This is because RNaseH can only cleave bonds between two ribonucleotides. The final ribonucleotide is removed by a 5’ exonuclease that degrades RNA or DNA from their 5’ ends.

TLS Online TPP Program

#Id: 5924

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 5925

#Unit 3. Fundamental Processes

Sequences that are involved with termination are called ter sites. A ter site contains a short, 23-bp sequence.

TLS Online TPP Program

#Id: 5926

#Unit 3. Fundamental Processes

The termination sequences are unidirectional; that is, they function in only one orientation. The ter site is recognized by a unidirectional contrahelicase