Reply #42: Sure, people have been working on chimeras for a long

[VegasWolf]

time. They just haven't translated to human genome transfer untill
recently. One study utilized chimeric mice to reveal clues
as to how the brain's clock "ticks" or synchronizes itself.
In mammals, the main circadian clock components reside in cells in the suprachiasmatic nucleus (SCN) of the brain.
The mice were genetically engineered using a standard technique for producing chimeric mice. The researchers combined eight-cell embryos from wild-type mice with cells from embryos that contained a mutant Clock gene, which produces a loss of circadian rhythms and a period length of 27-29 hours in homozygous animals (mice with two copies of the mutant gene).

I was involved in some neurological studies of mammalian clock
mechanisms back in the early 80's.