Question

In mammalian cells, sequence does not determine replication origin as in bacteria. What then might be structural features that can affect where replication origins will be?

Answer 1

In mammalian cell , DNA replication starts at ARS (Autonomous Replicating Sites) which are distributed over the genome

ARS is extended over 50 base pairs.

At ARS ,there are three regions known as A domain ,B1 domain ,B2 domain and B3 domain.

The A domain is 14 Bade pair "core region" contain A T repeats ,mutation in this region completely hampers the function of ARS .

B1 , B2 and B3 mutation partially inhibite the function of ARS.

If two of the B and the A domain are functional then ARS functions effectively.

So sequence is important for ARS in mammalian cells.

The A domain having 14 bp AT rich region on ARS is important for recognition by ORC(Origin recognition complex ,a group of protein involved in replication initiation on ARS site ,ORC specifically recognise A domain on ARS).