Question

In genetic fingerprinting, the ‘probe’ refers to
A. A radioactively labelled single stranded DNA molecule
B. A radioactively labelled single stranded RNA molecule
C. A radioactively labelled double stranded RNA molecule
D. A radioactively labelled double stranded DNA molecule

Answer 1

Genetic fingerprinting is nothing but the DNA fingerprinting technique. This was first developed by Sir Alec Jeffrys. DNA is the genetic material which is present in most of the living organisms with some exceptions of viruses where RNA is present. It is unique to each individual and can be used to know the identity. This technique is mainly done to know the genetic makeup of an individual organism.

Complete answer:
We know what DNA is and why the fingerprinting is done. Let us know about the steps involved in this technique. Firstly, we need to isolate DNA from the organism of interest and later using the endonuclease enzyme, the DNA is fragmented. Now, these fragments are separated using a technique called gel electrophoresis where agarose gel is used as a medium. Using an electric field or any capillary action, the DNA from the gel is transferred to a membrane like nylon. Now comes the probe. In the next step, a single stranded DNA fragment called probe is used to determine the nucleotide sequence of the sample that is complementary to the probe. This step is called hybridization. At last, these hybridized fragments are analysed using any imaging techniques. To detect the identity of the probe in the hybridized fragment, it is labelled with any radioactive substance. This is all about genetic fingerprinting.

Based on the above explanation,the correct option is A.

Note:
Probe is just the fragment of DNA with about 100 to 1000 bases and is simply a DNA oligonucleotide. If the probe is used to hybridize with the target DNA, it is referred to as Southern blotting technique. If it is used to hybridize with the target RNA ,then it is called Northern blotting. Probes are also used in Polymerase Chain Reaction.