Each person can have about 100 million different receptors, referred to as their T cell repertoire, with little overlap
even in identical twins.
There are many other traits that are not always the
same in identical twins, however, like eye color and fingerprints.
They suggest that future studies should investigate specific mechanisms that cause this so - called epigenetic
drift in identical twins.
A study of
aging in identical twins, published in Plastic and Reconstructive Surgery, found that up until twins turned 40, the heavier twin, with the higher BMI, looked older.
The relations among them may be far more complex and unsystematic, more like overlapping resemblances among members of an extended family than like minor modifications of one common and underlying genetic
structure in identical twins.
Other studies have found potential genetic links to explain why children of divorced parents have a higher risk of divorce and why divorce is common among identical twins (If one
twin in an identical twin pair divorced, it's much more likely that his or her twin would be divorced, too).
By examining
altruism in identical twins, who share nearly 100 percent of their genes, and fraternal twins, who share 50 percent of their genes, researchers can estimate the extent to which genes and the environment contribute to selfless inclinations and behaviors.
Consequently, if similar taste thresholds showed up dramatically more
often in identical twins than in fraternal twins, a person's perception of that flavor could probably be traced to genetics.
In 1924 Hermann Werner Siemens, a German, theorized that any condition that could be inherited should be more
concordant in identical twins than in fraternal twins.
The incidence of autism is
higher in identical twins, who share nearly 100 percent of their genes, compared with fraternal twins, who share only 50 percent, which indicates that there is a genetic component to the disorder.
«Identical twins have identical DNA,» Wright explains, «so if a gene is heritable, its expression will be more
similar in identical twins than in fraternal twins.
Gulati says a study looking at Lupus
occurrence in identical twins found that clinical manifestation of the disease occurred in both siblings only 24 percent of cases.
Despite the overall high similarity in X chromosome inactivation
patterns in identical twins at both ages 5 and 10 years, some identical twin - pairs had noticeably different patterns.
«We found that the methylation patterns matched almost
perfectly in identical twins, a degree of similarity that could not be explained by the twins sharing the same DNA,» says [researcher Robert] Waterland.
In 2005, a team of researchers at the Spanish National Cancer Research Centre led a study that analyzed DNA methylation patterns to see how they affected gene
expression in identical twins ranging in age from 3 to 74.
Endurance training with constant energy
intake in identical twins: changes over time in energy expenditure and related hormones.
We created a probiotic - rich version of this classic dip,
stirred in its identical twin flavor, and served it with raw veggies and healthy chips.
Analysis of the statistics clearly show the genetic basis for these disorders: For schizophrenia the
concordance in identical twins was 60 %, compared to only 10 % in non-identical twins, and the normal frequency being 1 % in northern European populations.
A similar thing occurs when you overfeed identical twins: one twin gains more fat than the other 10 The Response to Long - Term Overfeeding in Identical Twins
The team then compared how similar gut bacteria were
in identical twins (which have the same set of genes) and non-identical twins (who are assumed to share a very similar environment, but do not have exactly the same genes).
In the identical twin studies, they were «What's your favorite color?»
They found that, within twin pairs, the brighter twin tends to live longer than the less bright twin and this was much more pronounced in fraternal (non identical) twins than
in identical twins.