What causes differences in identical twins?
Many things can cause identiical twins to be different emotionally and physically that are not based on their genes. Additionally many twins while they share very similar DNA are not exact twins. To explain further, please check out epigenetics:
Epigenetics was coined in 1942 as a model of how genes within a multicellular organism interact with their surroundings to produce a phenotype. Because all cells within an organism inherit the same DNA sequences, cellular differentiation processes crucial for epigenesis rely strongly on epigenetic rather than genetic inheritance. Robin Holliday defined epigenetics as "the study of the mechanisms of temporal and spatial control of gene activity during the development of complex organisms." Thus, the word "epigenetic" can be used to describe any aspect other than DNA sequence that influences the development of an organism.
The modern usage of the word "epigenetic" is usually more narrow, referring to heritable traits (over rounds of cell division and sometimes transgenerationally) that do not involve changes to the underlying DNA sequence. The Greek prefix "epi-" in the word "epigenetics" implies features that are "on top of" or "in addition to" genetics, and the current usage of the word reflects thisÃ¢ï¿½ï¿½epigenetic traits exist on top of or in addition to the traditional molecular basis for inheritance.
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