[color=#000099][/color]Identical twins generate a lot of
curiosity. And a lot of
misconceptions! Parents of
multiples have probably not
given a great deal of thought to
their childrens' fingerprint
patterns, but the general public
has spent a lot of time
wondering about this topic.
So, do identical twins have
identical fingerprints? The basic
answer is NO. Identical -- or
monozygotic -- twins form when
a single fertilized egg splits in
two after conception. Because
they form from a single zygote,
the two individuals will have the
same genetic makeup. Their DNA
is virtually indistinguishable.
However, fingerprints are not an
entirely genetic characteristic.
Scientists love to use this topic as
an example of the old "nature vs.
nurture" debate. Fingerprinting,
along with other physical
characteristics, is an example of
a phenotype -- meaning that it is
determined by the interaction of
an indivdual's genes and the
developmental environment in
the uterus.
The ultimate shape of
fingerprints are believed to be
influenced by environmental
factors during pregnancy, like
nutrition, blood pressure,
position in the womb and the
growth rate of the fingers at the
end of the first trimester. Thus,
you will find similar patterns of
whorls and ridges in the
fingerprints of identical twins.
But there will also be differences
-- just as there are differences
between the fingers on any
individual's hands.

To a standard DNA
analysis, they would be
indistinguishable. Yet the parents
of twins can usually tell them
apart by subtle visual cues, and,
while their fingerprints are
generally similar, they are not
identical.
Fingerprints and physical
appearance in general are part
of an individual’s phenotype,
which arises from the interaction
of the individual’s genes and the
developmental environment in
the uterus. In the case of
fingerprints, the genes
determine the general
characteristics of the patterns
that are used for fingerprint
classification. As the skin on the
fingertip differentiates, it
expresses these general
characteristics. However, as a
surface tissue, it is also in contact
with the amniotic fluid in the
uterus. The fingertips are also in
contact with other parts of the
fetus and the uterus, and their
position in relation to uterus and
the fetal body changes as the
fetus moves on its own and in
response to positional changes
of the mother. Thus the
microenvironment of the
growing cells on the fingertip is
in flux, and is always slightly
different from hand to hand and
finger to finger. It is this
microenvironment that
determines the fine detail of the
fingerprint structure. While the
differences in the
microenvironment between
fingers are small and subtle, their
effect is amplified by the
differentiating cells and
produces the macroscopic
differences that enable the
fingerprints of twins to be
differentiated.
More generally, the environment
in the uterus affects the
phenotypic development of all
parts of the twin fetuses. Thus,
despite an identical DNA
structure of the two fetuses, a
very careful examination of
other physical characteristics will
show that twins are
systematically different,
although those differences may
be too subtle to detect without
careful measurement. This
process of differential
development continues
throughout life. As twins age,
they diverge more and more,
and in middle and old age will
look more like non-identical
twins, www.forensic-evidence.com/site/ID/ID_Twins.html