in which situation no leading strand is formed in DNA REPLICATION???????????????????????????????????????????????????

When replication is taking place from 3` to 5` direction then no leading strand is formed only lagging strand is formed

Actually it cannot happen.The enzyme DNA polymerase can work only in 5`to 3` direction . Therefore replication in 3`to 5` direction as said in the answer abovenis never possible .So if DNA replication is occurring,then both leading and lagging strands would be synthesized as DNA is a double stranded.Hope it helps