Properties of Genetic material :-

In some viruses RNA is the genetic material.
Example: Tobacco Mosaic viruses, QB bacteriophages etc.
The genetic material should have the following characteristics :-

1. Ability to replicate :- Both DNA and RNA have the ability to replicate and form complementary strand while protein doesnot have this ability.
2. Stability: The genetic material should be chemically and structurally stable So that the storage information in an organism can be passed
to next generation.
3 Mutation: The genetic material should have ability to mutate in order to evolve. RNA is more mutable as compared to DNA due to its instability.

RNA world

• RNA was the first genetic material.
• Walter gilbert (1986) hypothesized that once there was a RNA world. RNA used to act as a genetic material as well as a catalyst
  There are some important biochemicals reactions in living system that are catalyzed by RNA catalyst (ribozymes) and not byprotein enzymes.
• Example:- Ribonuclease P (cleavage), Peptidyl transferase (peptide bond formation) But RNA being a catalyst was reactive and hence unstable.

Replication :-

• It is a process of reproducing or creating a copy of genetic material.
• Watson and crick had immediately proposed scheme for DNA replication while proposing the double helical structure of the DNA.
• In replication 2 strands of DNA separate and both separated strands acts as a template strand.
• Watson and crick had immediately proposed scheme for DNA replication while proposing the double helical structure of the DNA.

Semi Conservative DNA Replication

The scheme suggested that the two strands would separated and act s a template for the synthesis of new complementary strand. After the completion of replication each DNA molecule would have one parental and one newly synthesized strand .this scheme was termed as semiconservative DNA replication.