Each person (except identical twins) has a unique genetic
profile, and the cells of a given person, irrespective
of tissue origin (they may come from bone, muscle,
blood, etc.), have the same DNA content.
Therefore, any type of sample/tissue can be used to generate
a genetic
profile.
The most efficient way to collect a DNA sample is through
buccal swabs, as it is non-invasive,
non-traumatic, fast
and a friendly way to obtain amounts of DNA sufficient
to perform tests. In the past, blood sampling used to
be the common method for sample collection; whereas
it can still be used, it does not have the aforementioned
attributes of buccal swabs.
During sample collection, three buccal swabs (similar
to Q-tips) are brushed gently yet firmly against the
patient's inner cheek; through swabbing, epithelial
cells shed from the inner cheek adhere to the swabs.
Then, DNA is extracted from these cells in the lab and
used to carry out the test.
Whenever a person cannot be present for direct sample
collection (e.g. the person is deceased, missing or
unwilling) other types of samples can be used, such
as semen, hairs with roots, nails, blood stains, cigarette
butts, toothbrushes, etc. These samples are considered
to be forensic samples, and while it is not guaranteed
(due to the nature, size and variability of these type
of samples), they often contain enough DNA to obtain
a partial or full genetic profile.
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