Index >> Gene Mutation >> Agents Producing Distortions in DNA

Agents Producing Distortions in DNA -

Certain flourescent acridine dyes such as proflavine and acridine orange cause mutations by insertion or deletion of bases.

Crick's work on acridine mutants has provided strong evidence for the genetic code.

The acridines are planer (flat) molecules, like the purine bases, and can be intercalated between the bases of the DNA helix. This distorts the structure of DNA and can result in deletion or insertion of bases during recombination.

During replication a base (X) is inserted at random opposite the acridine molecule in the new chain. In the next replication a complementary base (X) will pair with the newly inserted base.

Thus the new DNA has an additional base pair.

(ii) Intercalation resulting in deletion of base.

The acridine molecule may be inserted in the new chain during synthesis. This blocks the base in the template strand and does not permit any base to pair with it.

The chain produced is thus deficient in one base, and in the next replication produces DNA with a deficient base pair