An alteration in the base sequence of nucleic acid molecule is

Mutation

The answer is (4) mutation.

A mutation is a permanent change in the DNA sequence of an organism. This can be caused by a variety of factors, including environmental exposure, errors in DNA replication, and random chance. Mutations can have a variety of effects, ranging from no effect to mild to severe.

Dislocation, replication, and duplication are all processes that involve the copying of DNA, but they do not involve any changes to the base sequence. Therefore, the only option that is a change in the base sequence of a nucleic acid molecule is mutation.

Here are some examples of mutations:

• A single base substitution, in which one base is replaced by another.
• A deletion, in which a section of DNA is removed.
• An insertion, in which a section of DNA is inserted.
• A chromosomal rearrangement, in which the order of genes is changed.

Mutations can be harmful, beneficial, or neutral. Harmful mutations can lead to diseases, while beneficial mutations can give organisms a selective advantage. Neutral mutations do not have any effect on the organism.

Mutations are an important part of evolution. They provide the raw material for natural selection to work on, and they can lead to the emergence of new species.