Previous Year Question
Consider the following statements.
DNA Barcoding can be a tool to:
assess the age of a plant or animal.
distinguish among species that look alike.
identify undesirable animal or plant materials in processed foods.
Which of the statements given above is/are correct?
Only 1
Only 3
1 and 2
2 and 3
Correct Answer: D
Detailed Solution
DNA barcoding is a technique that uses a short and standardised DNA sequence from the genome of an organism for its identification. The obtained sequence is compared with sequences available in a verified reference database to determine the species of the organism.
Statement 1 is incorrect. DNA barcoding is generally used to identify the species of a plant or animal, not to determine its age. The age of an organism may be assessed on the basis of growth rings, teeth, bones, body size, developmental stage or other biological markers.
Statement 2 is correct. Two different species may appear almost identical externally. These may be described as cryptic species. Differences in their standardised DNA barcode regions enable DNA barcoding to distinguish between such species.
In animals, the mitochondrial DNA gene cytochrome c oxidase subunit I (COI) is widely used as a barcode region. In plants, the chloroplast genes rbcL and matK are used, whereas the Internal Transcribed Spacer (ITS) region is used in fungi.
Statement 3 is correct. The original morphological characteristics of food materials may be destroyed after processing, but if sufficient DNA remains available, barcoding can identify the animal or plant species present in them. It helps detect food adulteration, incorrect labelling and undesirable or prohibited biological materials.
Excessive heating, refining or chemical processing may severely degrade DNA, making identification difficult. Therefore, DNA quality, the reliability of the reference database and contamination control are important for the accuracy of the result.