Question

DNA fragment containing desired gene can be identified by

• A. Southern blotting
• B. PCR technique
• C. DNA probes
• D. Plasmid DNA

Answer 1

The correct option is C

DNA probes

The correct option is C.

The explanation for the correct option:

1. A probe refers to a single-stranded DNA sequence or RNA sequence, which can combine with its complementary sequence in a large fragment of DNA.
2. The probe is either tagged radioactively or fluorescently labeled for easy detection.
3. The probes, which are mainly made up of DNA sequences are used to determine the gene of interest in a fragment of DNA.
4. The DNA fragments containing the DNA probe are then amplified by the polymerase chain reaction (PCR), separated by gel electrophoresis, and transferred to nylon membranes through southern blotting.

The explanation for the incorrect options:

Option A:

1. A procedure that is used in molecular biology for the detection of a particular sequence of DNA in the samples of DNA is southern blotting.
2. The technique is used after the process of gel electrophoresis.
3. An approach in which mixtures of DNA, proteins, or DNA are separated based on their molecular sizes is gel electrophoresis.

Option B:

A laboratory technique that is used for amplifying or producing millions to billions of copies of a particular DNA segment is PCR or polymerase chain reaction.

Option D:

1. A small circular DNA molecule found in bacteria and some other microscopic species is known as a plasmid.
2. They are physically different from the DNA of chromosomes and replicate independently.
3. They mainly work to carry antibiotic-resistant genes and spread them in the whole animal or human body.

Final answer: DNA fragments containing the desired gene can be identified by DNA probes.