Identical twins...are they really identical?

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Like many identical twins reared apart, Jim Lewis and Jim Springer found they had been leading eerily similar lives. Separated four weeks after birth in 1940, the Jim twins grew up 45 miles apart in Ohio and were reunited in 1979. Eventually they discovered that both drove the same model blue Chevrolet, chain-smoked Salems, chewed their fingernails and owned dogs named Toy. Each had spent a good deal of time vacationing at the same three-block strip of beach in Florida. More important, when tested for such personality traits as flexibility, self-control and sociability, the twins responded almost exactly alike. This came from an article in Time Magazine, some time ago I might add

There are many other fantastical identical twins tales
"My God, that is unreal we haven't seen each other for 30 years and you like a Peak Frean biscuit with your morning coffee. So do I!!, (That is a very common brand of biscuit in the UK)
"And your second wife was called Betty...so was mine!!!
(Betty is one of the most common names).
 "And you called your dog 'Prince', and its an Alsatian....this is getting spooky."
 (Not quite for don't all males of a certain class have Alsatian dogs and further universally call them 'Prince'.)
And you use that brand of toothpaste...and you use a knife and fork when you eat, so do I...I don't believe it..."

Neither do we,  for modern scientific research has made the populace less credulous.

 

But are Identical twins Identical?  Hey,why not, after all, they derive from just one fertilized egg, argue the credulous
 

But more recent research shows that identical twins are rarely completely the same. Until recently, any differences between twins had largely been attributed to environmental influences (otherwise known as "nurture"), but a recent study contradicts that belief.

Normally people carry two copies of every gene, one inherited from each parent.

However research has show that there are, regions in the genome that deviate from that two-copy rule, and that's where you have copy number variants.  These regions can carry anywhere from zero to over 14 copies of a gene.

For example, one twin may be missing some genes on particular chromosomes that indicated a risk of leukemia, which he indeed suffered. The other twin did not.

Latest research calls into question the many findings of previous twin studies
that assumed identical twins were indeed identical.