The detection rate
among the discordant Parkinson twins suggests an even
higher figure, but this is within a selected, discordant
group and thus might represent a mixture of phenotypically
relevant, as well as random, and phenotypically
neutral CNV events.)

Somatic mosaicism is usually defined
by the presence of genetically distinct populations
of somatic cells in a single organism. Any genetic difference
between MZ twins represents an extreme example
of somatic mosaicism.