The chemical structure of DNA in everyone is the same. The only
difference is the order of the base pairs. Like in fingerprinting,
there are so many millions of base pairs in everyone’s DNA that every
person has a unique sequence.
Every person could be identified using the sequence of their base
pairs. However, there are so many base pairs in every person that this
would be very time consuming. Repeating patterns in DNA allow
scientists to use a much shorter method.
These patterns help to determine if two DNA samples can from the same
person, related people or non-related people. The sequences analyzed
by the scientists are patterns that are known to vary greatly among
individuals. This allows the scientist to assign a probability to a
match. Since 1987, more than 150 cases have been decided with the
assistance of DNA fingerprint evidence.
DNA base pair pattern identification has many uses. DNA
patterns are inherited from parents, and can therefore be used to
indicate paternity and maternity. They can be to confirm legal
nationality and determine biological parenthood.
DNA analysis can be used to determine whether or not a
suspect was at a crime scene. DNA can be found in blood, hair, skin
cells, semen or other genetic evidence left at a crime scene. It can
also be used to determine the identity of a victim.
DNA fingerprinting is an important advance in the
diagnosis of inherited disorders because early detection of these
disorders allows the parents and medical staff to prepare for proper
treatment of a child. This research can be extended into developing
cures for inherited disorders.
DNA fingerprinting is a laboratory procedure that can be
done in six steps. DNA must be recovered from the cells or tissues of
the body. Restriction enzymes are used to cut the DNA at specific
locations according to the DNA sequence at that location. The DNA
pieces are sorted according to size through a process called
electrophoresis in which the particles are passed through seaweed
agarose to determine particle sizes. The DNA is transferred to nylon
by placing the sheet on the gel and letting them soak. Radioactive or
colored probes are added to the nylon sheet and a pattern is produced.
This pattern is called a DNA fingerprint and is formed because each of
the colored probes sticks in specific places on the nylon sheet. A
final DNA fingerprint is made through the use of several probes at the
same time to form a code.
There are some problems with DNA fingerprinting. The
repeating patterns can only present a probability of the DNA match
retrieved. The probability might be 1 in 20 billion, so it is a
reasonable match, but unlike a fingerprint, repeating DNA patterns are
not completely unique to each person. A probability might also be 1 in
20, and this would leave a lot of doubt. The probability values
assigned help to determine the chance that the DNA fingerprint belongs
to the person in question.
There is also room for error in the probing techniques
used to acquire the DNA pattern. This presents a problem for court
cases because it could give false results.
DNA fingerprinting is useful because DNA structure can not
be altered. Unlike fingerprints, there is no way to change the DNA
fingerprint. It cannot be altered by any known treatment. It is the
same for every cell, tissue and organ in a person. DNA fingerprinting
is also a way of giving a quantitative assessment to an identification
match. This allows for a better idea of the reliability of the