Choose the correct pair of characteristics of molecular probe is:

I. A molecular probe is a single-stranded DNA or RNA labeled with a radioactive molecule.

II. A molecular probe is a double-stranded DNA labeled with a radioactive molecule.

III. The molecular probe does not exhibit complementarity with the mutated gene.

IV.  It shows complementarity with mutated gene.

I and III

In genetic research and molecular biology, a technique called autoradiography is used to detect specific DNA or RNA sequences in a sample. To do this, a molecular probe, which is a single-stranded DNA or RNA molecule labeled with a radioactive marker, is employed. The radioactive probe is designed to be complementary to a specific target sequence in the DNA of interest.

When the radioactive probe is allowed to interact with the DNA in a clone of cells, it will seek out and bind to its complementary DNA sequence. This binding is known as hybridization. The radioactive signal from the probe is then captured on a photographic film through autoradiography.

Now, suppose the clone of cells contains a mutated gene, which differs in sequence from the normal or wild-type gene. Since the probe is designed to be complementary to the normal gene sequence, it will not have the same complementary sequence to the mutated gene. As a result, the probe will not be able to hybridize with the mutated gene, and no radioactive signal will be detected on the photographic film for that particular clone.

In contrast, clones with the wild-type gene will exhibit a signal on the photographic film because the probe successfully hybridizes with the normal gene sequence.

By analyzing the autoradiogram, researchers can distinguish between clones with the wild-type gene and clones with the mutated gene, helping them identify and study genetic variations or mutations in a population of cells or organisms. This technique is fundamental in genetic research and plays a critical role in identifying and characterizing genes associated with specific traits or diseases.