Question

where DnaG(primase) bind and make primer on the template DNA?

usually the length of the okazaki fragment is around 1000-2000bp.

how primase make primase on every 1000-2000bp.

also, as primer is a kind of RNA polymerase, is there any specificity for binding on DNA?

if so, how the length of the okazaki fragment could be relatively constant?

how primase make *primase-> how primase make *primer

Answer 1

Where DnaG (primase) bind and make primer on the template DNA?

DnaG is a bacterial DNA primase which is encoded by the dnaG gene. The enzyme DnaG, synthesizes oligoneucleotides which are short strands of RNA during DNA replication. Synthesis of oligonucleotides involves five discrete steps: 1) binding of templates. 2) NTP (Nucleoside triphosphate) binding. 3) Initiation. 4) Extension to form a primer and 5) Transfer of primer to DNA polymerase III.

DnaG performs this synsthesis process near the replication fork that is formed by DnaB helicase during DNA replication.

Usually the length of the okazaki fragment is around 1000-2000bp.

How primase make *primer on every 1000-2000bp?

During the DNA replication process, replication fork is created by the enzyme DNA helicase by unwinding of double helix DNA. Following this fork, a new complementary strand begin to form by DNA primase and then DNA polymerase enzyme. In prokaryotes, primase binds to the DNA helicase and form a complex that is called the primosome. Primase get activated by the helicase and then synthesizes a short RNA primer which is approximately 11 ±1 nucleotides long. DNA polymerase then elongates the chain by adding new nucleotides.

Primase and DNA polymerase can work in the 5’ to 3’ direction only, as a result the two unwound template strands are replicated in different ways. RNA primers are added onto the lagging strand by Primase and begin which synthesis of Okazaki fragments from 5' to 3'. RNA primers formation rate in lagging strand is much lower than DNA synthesis on the leading strand. As DNA polymerase on the lagging strand has to be continually recycled to construct Okazaki fragments following RNA primers it makes the lagging strand synthesis process slower. But primase acts as a temporary stop signal that halts the progression of the replication fork during DNA replication process and thus prevents the leading strand from overtaking the lagging strand.

Also, as primer is a kind of RNA polymerase, is there any specificity for binding on DNA?

Primers are short strands of RNA or it can be DNA in some organisms, which are synthesised during DNA replication by Primase. This primase enzyme is a type of RNA polymerase. RNA polymerase involves in DNA transcription where as Primase involved in DNA replication. Replicative DNA polymerases cannot initiate the DNA strand synthesis without initial RNA OR DNA primers as Primase catalyses the synthesis of Primers.

How the length of the okazaki fragment could be relatively constant?

RNA primers are added onto the lagging strand by Primase and begin which synthesis of Okazaki fragments from 5' to 3'. RNA primers. As DNA polymerase on the lagging strand has to be continually recycled to construct Okazaki fragments following RNA primers it makes the lagging strand synthesis process slower. Primase acts as a temporary stop signal that halts the progression of the replication fork during DNA replication process and thus prevents the leading strand from overtaking the lagging strand. Because of these phenomena the length of the okazaki fragment could be relatively constant.