Question

Alec Jeffreys developed the DNA fingerprinting technique. The probe he used was
A. Ribozyme
B. Sex chromosomes
C. SNP
D. VNTR
E. rDNA

Answer 1

Hint: DNA fingerprinting as the name suggests is the process by which certain unique aspects of a person’s DNA are identified. These specific fragment lengths within their DNA were unique to each individual. These fragments repeated themselves at variable length throughout the DNA. Based on the uniqueness, the DNA of any individual can be identified.

Complete answer: During the 1980s, it was well established that DNA is a unique biomolecule present for everyone. It was during 1983 when Alec Jeffreys obtained the patent to use DNA as a method to identify individuals by using certain probes. He identified that certain regions in the DNA were repeated randomly throughout and the number of repeats was unique to each individual. Thus, by identifying the number and position of these repeats on DNA, one can identify the person accurately. These repeats varied in each individual and occurred tandemly at different locations of the DNA and thus were named Variable Number of Tandem Repeats (VNTRs). The first step involves isolation and extraction of the DNA which is obtained from cheek swabs, blood, saliva, sweat, hair, etc. Once the DNA has been isolated the repeats need to be separated to identify their number and position, which is done by restriction enzymes also known as molecular scissors. This is known as RFLP analysis (Restriction Fragment Length Polymorphism). Once this is performed, the DNA needs to be amplified to visualize the repeats on a gel or film and thus a PCR (Polymerase Chain Reaction) reaction is performed, which yields millions of copies of the DNA fragments. The amplified DNA is run on a gel and a unique banding pattern emerges, which can be cross-referenced with other DNA samples to identify the person.
Therefore, the correct answer is option D.

Note: The process of DNA fragmentation is also known as DNA profiling. It is widely used in forensic sciences. It is believed that the DNA banding pattern is unique and is only similar in the case of identical twins. The first used probe for DNA fingerprinting was VNTRs but today STR or Simple Tandem Repeats are also used as probes. Similarly, RFLP can be replaced by AFLP which stands for Amplified Fragment Length Polymorphism, which specifically only amplifies the fragments necessary for analysis.