Newly formed DNA copies may not be identical at times. Gives one reason.

The DNA copies are produced during the process of cellular division. The new DNA copies which are synthesised during replication may not be identical to the original one. This may be due to the introduction of mutations during the replication process. Mutations are random genetic changes. There are repair mechanisms which correct the mutations incorporated in the DNA. However, there may be some errors which remain in the new DNA. So, it is not necessary that the copies may be identical at times.