Ars: A paper in this week’s PNAS describes a system that may allow us to get around this limitation. The new method takes a protein from a virus that infects bacteria and cuts it in two, making a pair of genes (A and B) that each produce part of the mature protein. The two parts then act as a biological version of an AND logic gate, with output (in the form of protein activity) present only when both A and B interact. When either or both A and B are missing, the output is off.
In biological terms, the inputs usually involve a simple molecule that can be sensed by proteins inside a bacteria. This paper, for example, used two kinds of sugars (arabinose and lactose). When the sugars are present, they attach to proteins inside the cell, activating genes that are controlled by those proteins. To make an AND gate, you need to design a bit of biology that can respond to both of these signals—it should be active only when both a gene regulated by arabinose and a gene regulated by lactose are each active.
Most of you don’t understand a word of that. That’s why I’m going to have a lot more money than you.