At the molecular level, what’s really going on as the marble rolls down the slope is that different genes are being switched on and off, guided by transcription factors, sirtuins and other enzymes such as DNA methyltransferases (DNMTs) and histone methyltransferases (HMTs), which mark the DNA and its packing proteins with chemical tags that instruct the cell and its descendants to behave in a certain way.
The code.how differences happen
