Question

What is ‘ori’?

Answer 1

Hint: Replication in the animals or eukaryotes help in the duplication of the DNA material while being transferred to the next generations. There are different points at which the replication starts. Their number varies from prokaryotes to eukaryotes.

Complete answer:
Ori is the short form of origin of replication. It is the sequence of the genome at which the replication starts. This sequence is very particular.
The passing of genetic material from generation to generation requires the duplication of DNA by semiconservative replication before the cell division.
This semi-conservative replication starts at the ori sites which indicate the starting site for the replication.
In the plasmid, at the ori site, it starts to reproduce itself to survive within the cells. The replicons of the plasmid are different from the chromosomal DNA but still depend on the host machinery to make their copies.
In the eukaryotes, there are 30,000 – 50,000 ori sites in humans. The replication fork forms at the replication step in humans. Being there many ori sites in the DNA sequence, there occur so many replication forks.
For the small viruses, plasmid and DNA, the single site of origin of replication is enough for the process. The short fragments of DNA are known as Okazaki fragments. This is the lagging strand.

Note: There is only one site of replication in prokaryotes. They are the arrays of repeated sequences. The replication in them occurs in the opposite direction in the cell cytoplasm. But in the eukaryotes, it is unidirectional and there are many points of replication.