Question

why RNA were used as primer in DNA replication..??

Answer 1

DNA polymerase cannot bind on single-stranded DNA. DNA primers add RNA primer so that DNA polymerase can bind and add nucleotide.

Answer 2

Yukitou is correct. DNA Polymerase cannot bind to single stranded DNA - it can only bind to a few complementary bases already on the strand it is trying to transcribe. This primer is produced by RNA polymerase, after which RNA pol dissociates, DNA pol binds, and after completing replication, the RNA primers are removed and replaced with DNA.