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Scientists Invented AI Made From DNA


From: "Dave Farber" <farber () gmail com>
Date: Wed, 11 Jul 2018 09:17:18 +0900




Begin forwarded message:

From: Dewayne Hendricks <dewayne () warpspeed com>
Date: July 11, 2018 at 8:00:32 AM GMT+9
To: Multiple recipients of Dewayne-Net <dewayne-net () warpspeed com>
Subject: [Dewayne-Net] Scientists Invented AI Made From DNA
Reply-To: dewayne-net () warpspeed com

Scientists Invented AI Made From DNA
Researchers made a neural network out of DNA that can recognize handwritten numbers.
By Daniel Oberhaus
Jul 9 2018
<https://motherboard.vice.com/en_us/article/594mvz/ai-made-from-human-dna>

Last Wednesday, researchers at Caltech announced that they created an artificial neural network from synthetic DNA 
that is able to recognize numbers coded in molecules. It’s a novel implementation of a classic machine learning test 
that demonstrates how the very building blocks of life can be harnessed as a computer. 

This is pretty mind blowing, but what does it all mean? For starters, “artificial intelligence” here doesn’t refer to 
the superhuman AI that is so beloved by Hollywood. Instead, it refers to machine learning, a narrow form of 
artificial intelligence that is best summarized as the art and science of pattern recognition. Most of the cutting 
edge advances in machine learning involve artificial neural networks, which are a type of computing architecture 
loosely based on the human brain. These neural networks are fed a lot of data as input and then taught how to perform 
some task with that data; sometimes humans help to guide the algorithm’s learning, and sometimes not.

This is effectively what the Caltech researchers designed, but instead of using silicon and transistors, they used 
DNA and test tubes as their neural network’s hardware.

All DNA is composed of four basic nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T). Strands of 
these nucleotides can bond with other strands of these nucleotides to form the double helix of DNA, but can only bind 
in specific combinations (i.e., A-T or C-G). This predictable pattern of combination makes these nucleotide strands 
ideal computing devices, which can be designed so that they produce specific chemical reactions in the presence of 
various molecules.

The Caltech researchers applied this sort of DNA-based computer to one of the classic tests in computer vision 
research: teaching an algorithm how to recognize handwritten numbers. This is tough for a computer to do because 
humans all write the number four slightly differently. Humans are hardwired to easily see the similarities between 
the ways different people write four, but machines don’t have such biological luxuries. By feeding an artificial 
neural network a ton of handwritten examples of the number four, however, an algorithm can “learn” to generalize 
qualities from individual examples and form an abstract idea of what a written four looks like. The next time the 
algorithm encounters something that looks like a four, it will compare this to its abstract representation of four 
and if it’s a close enough match, it will conclude that it is looking at a four.

In 2011, Caltech bioengineer Lulu Qian created the first artificial neural network out of DNA, but it could recognize 
only a handful of patterns. In the work unveiled last week, one of Qian’s graduate students, Kevin Cherry, has 
considerably advanced this technique by applying it to the recognition of handwritten “molecular numbers.” Each 
molecular number was based on a handwritten number translated into a 20-bit pattern in a 100-bit (10x10) grid. Each 
of the bits on the grid was represented by a molecule of DNA, and these molecules of DNA were assigned a place on a 
conceptual 10x10 grid before being mixed together in a test tube.

The DNA in the test tube doesn’t resemble a grid—it’s all mixed up—and so a molecule’s place on the grid was 
determined by the concentration of each molecule in the test tube. The DNA neural net was a strand of DNA that 
produced a specified reaction when added to the test tube only if the 20 DNA molecules assigned to represent a given 
number are arranged (i.e., in the appropriate concentrations) so that they form that number when translated onto the 
10x10 grid.

Cherry began his experiment by building a neural net that could distinguish between handwritten sixes and sevens that 
had been translated into molecular structures. He tested this approach on 36 different handwritten versions of the 
same numbers and in each instance the DNA neural network was able to recognize them. Cherry used a “winner take all” 
approach to allow DNA neural nets to distinguish between numbers by synthesizing a so-called “annihilator” molecule.

"The annihilator forms a complex with one molecule from one competitor and one molecule from a different competitor 
and reacts to form inert, unreactive species," Cherry said. "The annihilator quickly eats up all of the competitor 
molecules until only a single competitor species remains. The winning competitor is then restored to a high 
concentration and produces a fluorescent signal indicating the networks' decision.”

[snip]

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