A single stranded DNA or RNA tagged with a radioactive probe is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using ___________.

Autoradiography

The correct answer is Option (3) → Autoradiography

A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.

1. Polymerase Chain Reaction (PCR) is a laboratory technique used to amplify and analyze DNA sequences. It is used to generate multiple copies of a specific DNA sequence. PCR amplifies DNA by cycling through repeated steps of denaturation, annealing, and extension, creating millions of copies from a small DNA sample.It is commonly used for applications such as paternity testing, detection of mutations in genes (including suspected cancer patients), and identifying genetic disorders. 

2. Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis. ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.

4. The process of cutting DNA using restriction endonucleases results in the formation of DNA fragments. These fragments can be separated using a technique called gel electrophoresis.