Lack of environmental constraints hypothesis suggests preadaptation of some invaders to existing environmental conditions.

With few limitations to many abiotic environments, these invaders can grow quickly and outcompete native species

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

TLS Online TPP Program

#Id: 5927

#Unit 3. Fundamental Processes

In E. coli, two clusters of five ter sites each, including terK, -I, -E, -D, and -A on one side and terC, -B, -F, -G, and -H on the other, are located 100 kb on either side of this termination region.

Each set of ter sites is specific for one direction of fork movement

TLS Online TPP Program

#Id: 5991

#Unit 3. Fundamental Processes

Eukaryotic replication is similar in most aspects to bacterial replication. It is semiconservative, bidirectional, and semidiscontinuous.