Information theory bogosity. Or, fun with numbers.
A modern computer uses a 64-bit word for
computations. Each bit in the word has 2 possible states, so at any given
time a word comes from a space of 2^64 possible combinations.

Further, let's be generous, and give the computer a main memory of 2^36
words. Thus, at any one time the total state space for a computer is a
state with (2^36)*(2^64) = 2^100 possible combinations. The memory here is 2^6
gigawords, or 2^9 gigabytes = 512 gigabytes of main memory (I said we were
being generous, we'll see why in a minute).

Now, DNA is a chemical word of length order 3 billion bits for humans.
That is, a human chemical word is in a state of 2^(3,000,000) possible
combinations. Further, there are on the order 40 trillion (40*10^12) cells
in a human body. This is approximately 2^40 possible words, so that there are
of order (2^40)*(2^100)^(10,000,000) possible combinations.

That is, to fully (with arbitrary fidelity) know every DNA state in a human
body would take 16*10,000,000 = 160,000,000 64-bit computers each with 512
gigabytes of main memory. To the orders considered here, the human brain and
the human body have no meaningful difference in the number of cells.

So, in one tortured pass at the numbers, specifying the DNA state  of a given
human body at any instance of time
would require over 160,000,000 computer cores each with 512 gigabytes of main
memory.

A computer that can address, and compute in a meaningful manner,
simultaneously, 1000 terabytes of main memory? For a current standard, it
takes most of a day to transfer 1 terabyte between two hard drives, even with
fast local access. And Moore's law stopped some ten years ago.

This is just to specify the DNA state. There are approximately 10 billion
proteins in each cell in the human body. So, to specify both the DNA state
and the *proteins that read the DNA and make the cell work* requires on the
order (10^10)*(10^8) = 10^18 = 1 billion billion 64-bit computers each with
512 gigabytes of main memory.

There are 7 billion humans on the planet now. So, in order to compute at
the equivalent to a single human body chemical calculation would require
on the order of 100,000,000 times as many computers as have ever been
constructed at the time of this writing.

General AI in the sci-fi sense doesn't seem very possible, given this. But
I wonder.

This may give you nightmares, or it might be your fondest dream. But, if you
look at computer-enhanced/expanded intelligence, then AI is pretty close to
reality, at least the first halting steps out of the laboratory, with
lightning and bolts in the neck and the Elsa Lancaster wig and everything.

It's called the Internet.