12. Other enzymes and non-enzymatic proteins required for DNA replication.

Question 1

Basic types of replication

Answer 1

According to how the replication fork interacts with the matrix, there are 3 models of replication:
-Eye (bubble)
-Rolling circle
-D-loop

Question 2

Eye (bubble) replication:

Answer 2

Main Type: Common in both linear and circular DNA.

Mechanism: Bidirectional replication starting from an origin, forming a bubble (eye) that enlarges as replication proceeds.

Question 3

Rolling Circle Replication (RCR)

Answer 3

Usage: Plasmids, bacteriophages, circular RNA.

Process:

-Endonuclease cleaves one strand.
-DNA polymerase replicates along the template, pushing out the 5’ end.
-Okazaki fragments form the lagging strand.
-Endonuclease cuts and ligase closes rings; without cutting, long strands form (gene amplification).

Question 4

D-loop Replication

Answer 4

Usage: Mitochondria and plastids.

Process:

-Starts on H-chain, displacing old strand.
-Replication starts on L-chain after half is covered.
-No lagging strand, single primer used.