Video Transcript
A man died in a fire and the police
are trying to identify the body. After an initial inspection, it was
found that the victim’s body was entirely burnt. Which of the following samples
could the authorities use to search for the victim’s identity in their
databases? (A) The victim’s fingerprints. (B) A DNA sample from the victim’s
corpse. (C) A facial picture of the
victim. (D) The victim’s footprints.
This question asks us about a way
for authorities to identify a victim whose body has been completely burnt. Since the victim in our question
had their entire body burned, we would not expect to be able to identify them based
on their physical appearance. However, there are other ways to
identify human remains through a process called DNA fingerprinting. This can be used because DNA is a
very stable molecule.
We can do this by extracting the
DNA from some of the cells of the victim’s body. This DNA contains a sequence of
nucleotides that is unique to this particular individual. Special enzymes called restriction
enzymes act as molecular scissors that can be used to cut the DNA at specific sites
in the victim’s DNA. These cuts create fragments of DNA
that are a specific size. These fragments and their size are
unique to this individual. Another individual would have a
different sequence of DNA that would create different fragment sizes after
restriction enzyme cutting.
We can arrange these fragments
based on their size using a technique called gel electrophoresis. This separates the fragments and
creates a unique pattern that we call a DNA fingerprint. A different person would produce a
different DNA fingerprint. Because this DNA fingerprint is
unique to the burnt victim, it can be used to identify them from police
databases.
Therefore, the sample that can be
used to identify the burnt victim is given by answer choice (B): a DNA sample from
the victim’s corpse.
