Answer by Anand Mallaya:

DNA may not be a Turing machine, but it can,very much likely, be part of a Turing Machine.

A Turing machine consists of

1. ATape– A tape divided in to cells. Each cell capable of holding a symbol from a finite set of alphabets.

2. AHead– Which can move left or right through the tape and read the alphabets in the tape.

3. AState Register– A register which stores the state of the machine.

4. AnInstruction Table– Which based on the state of the machine and the alphabet on the cell in which the head is currently reading, performs one of the set of predetermined actions.

Examples of instructions can be like

Write an alphabet on the cell

move the head right or left

stay on the same cell etc.If you compare this with a biological cell, we can find many interesting features of the cell which can be related to a turing machine.

Tape <=> DNA

Head <=> Ribosome

State Register <=> RNA

States <=> Amino acid

Instruction Table <=> DNA codon table

Ouput Tape <=> Proteins

Formal Definition of Turing MachineA (one-tape) Turing machine can be formally defined as a 7-tuple

where

is a finite, non-empty set of

statesis a finite, non-empty set of

tape alphabet symbolsis the

blank symbol(the only symbol allowed to occur on the tape infinitely often at any step during the computation)is the set of

input symbolsis a partial function called the

transition function, where L is left shift, R is right shift. (A relatively uncommon variant allows "no shift", say N, as a third element of the latter set.)is the

initial stateis the set of

finaloraccepting states.

The Function

The function being performed is finite time and is the Protein biosynthesis

The Instruction SetNotable differences are

- The head only moves in one direction.
- The output tape is different from the input tape