A single stranded DNA or RNA, tagged with a radioactive molecule is called as:

Probe

The correct answer is Option (4) → Probe 

In autoradiography, a single-stranded DNA or RNA molecule, labeled with a radioactive probe, is allowed to hybridize to its complementary DNA in a clone of cells. The detection of this hybridization is carried out using photographic film.

Clones that have the mutated gene will not appear on the photographic film because the labeled probe used in autoradiography specifically binds to the complementary sequences in the DNA or RNA.

If the gene in the clone is mutated, the probe will not have complementarity with the mutated gene, and as a result, no signal will be detected on the photographic film for that specific clone.