Video Transcript
What is meant by DNA fingerprinting? (A) DNA fingerprinting is a technique commonly used in the lab to separate DNA
molecules according to their size. (B) DNA fingerprinting is a technique used to detect the proteins produced by
thousands of genes at the same time. (C) DNA fingerprinting is a technique that analyzes the patterns produced by unique
repetitive DNA sequences in the genome of an individual. (D) DNA fingerprinting is a technique used to make multiple copies of a segment of
DNA.
This question asks us about DNA fingerprinting, which has many important
applications. It is a technology that takes advantage of the unique sequence of nucleotides present
within the cells of each individual.
You may recall that all living organisms contain DNA. This DNA is made up of repeating subunits called nucleotides that contain different
nitrogenous bases. These can be guanine, cytosine, adenine, or thymine. In humans, each cell contains billions of these nucleotides and the sequence of these
nucleotides is 99.9 percent the same between two individuals.
Our total amount of DNA, or our genome, is billions of nucleotides. So this 0.1 percent difference actually represents millions of nucleotides that are
different between individuals. Many of these differences can occur in repetitive sections of our DNA, which
represent more than half of our genome.
Let’s indicate some of these differences as black dots in the DNA for person B. Here, you can see one nucleotide from person A is an adenine, while this is a
cytosine in person B. In order to see these differences, we can use special enzymes called restriction
enzymes that can cut DNA at specific nucleotide sequences.
Let’s say this restriction enzyme only cuts the DNA sequence GAATTC. The DNA in person A has this sequence at this particular site, so it will be cut by
the restriction enzyme. However, person B has a different nucleotide at this position, so the restriction
enzyme won’t cut the DNA at that point. Because of these differences in the two sequences, this results in different cutting
patterns throughout the DNA of person A and person B. These cuts produce fragments of DNA. And because there are different cutting patterns between these DNA sequences, there
will be differently sized fragments.
Using a special technique called gel electrophoresis, these fragments can be arranged
by their size in a gel and photographed. This pattern of fragments that we see in the gel is unique to each individual and is
why we call this a DNA fingerprint.
Now that we understand what is meant by DNA fingerprinting, let’s go through the
answer choices and choose the best option.
Answer choice(A) describes only a part of the DNA fingerprinting procedure that
relates to gel electrophoresis. So this answer is incorrect.
Answer choice (B) does not describe what is meant by DNA fingerprinting. So this is incorrect.
Answer choice (C) seems to be the correct answer, but let’s look at the last option
before making our final decision.
Answer choice (D) does not describe what is meant by DNA fingerprinting. So this is incorrect.
Therefore, the option that best describes what is meant by DNA fingerprinting is
given by answer choice (C). DNA fingerprinting is a technique that analyses the patterns produced by unique
repetitive DNA sequences in the genome of an individual.
