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Offline neilep

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How Identical are identical twins ?
« on: 05/05/2007 21:23:22 »
Do they have the same fingerprints ?

The same allergies ?

Fears and anxieties ? (assuming bought up in an identical way)


If not ?...then why are they called  " Identical " twins ?


 

paul.fr

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How Identical are identical twins ?
« Reply #1 on: 06/05/2007 08:29:24 »
well they may look the same, but.

Identical, or monozygotic, twins develop from a single egg/sperm combination that splits a few days after conception. Their DNA originates from a single source, thus their genetic makeup is the same and the characteristics that are determined by genetics will be similar. Monozygotic twins are always of the same gender, except in extremely rare cases of chromosomal defect.

On the other hand, fraternal, or dizygotic multiples form when two separate eggs are fertilized by separate sperm in a single ovulation cycle. They are no more alike than any sibling set, sharing about 50% of their genetic markers in a unique combination of genes from both parents.

Environmental Differences

While identical twins form with the same set of genes, human development is not just genetic. The environment also has an impact So, beginning in the early environment of the womb, external influences can change the appearance of twins. For example, some monozygotic twins share a placenta. One twin may have a more advantageous connection to the placenta, receiving the first run of nutrients. This situation can cause a size discrepancy between the babies, a physical difference that continues as they grow up. Twin-to-Twin Transfusion Syndrome (TTTS) is another condition that affects twins in the womb, and can impact their development.

While most twins grow up in the same home environment, there are many circumstances that create differences in the childrens' appearances, personalities, and interests. As the twins approach the teen years, they may even seek to establish dissimilar qualities in order to establish individual identities.

Epigenetic Differences

Scientists have offered a new explanation for the differences between identical twins. Epigenome refers to natural chemical modifications within a person's genome (genetic material). As an article in the New York Times explains, they "act on a gene like a gas pedal or a brake, marking it for higher or lower activity."

A study conducted by a team of researchers at the Spanish National Cancer Center in Madrid concluded that, while identical twins are born with the same epigenome, their epigentic profiles begin to diverge as they age. The differences increase as twins live longer and spend more time apart. The scientists offered two theories to explain this phenomenon. First, that epigentic marks are removed randomly as people age. Secondly, environmental influences change the pattern of epigentic marks.

In a Washington Post article Dr. Manel Esteller, lead researcher, said that "small epigenetic events before birth probably account for many of the minor distinguishing differences in the appearance, personality and general health of young twins." That's

An international team of scientists studied the DNA of more than forty pairs of twins. The research is significant because changes in the epigenome may be responsible for the development of disease, like cancer. It's hoped that further study of the epigenome in identical twins will help researchers pinpoint factors that contribute to cancer.

 

Offline iko

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How Identical are identical twins ?
« Reply #2 on: 06/05/2007 22:29:17 »
Do they have the same fingerprints ?
The same allergies ?
Fears and anxieties ? (assuming bought up in an identical way)
If not ?...then why are they called  " Identical " twins ?

Yap. But what about fingerprints?   ???


One shoot on Google, and that's it: the answer is NO.


Twins And Fingerprints

from "about: Parenting of multiples"  by Pamela Prindle Fierro

Do Identical Twins Have Identical Fingerprints?
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 individual'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 partterns 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.

more reading from:  http://multiples.about.com/cs/funfacts/a/twinfingerprint.htm


« Last Edit: 06/05/2007 22:39:30 by iko »
 

Offline Zoey

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How Identical are identical twins ?
« Reply #3 on: 14/05/2007 04:17:24 »
 As a kid we had neighbors who were mirror twins; one was left handed, the other right handed. It was nearly impossible to tell them apart. One was good in math, the other English so one went to math class twice a day the other English. The teachers didn't catch on.
 

Offline kdlynn

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How Identical are identical twins ?
« Reply #4 on: 14/05/2007 04:22:20 »
that would have been fantastic! i wish i had a math twin! lol
 

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How Identical are identical twins ?
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