9. DRAWBACKS :-

9. DRAWBACKS :-
1) Occasionally Slow:
The speed of each process in DNA Computing is still an open issue until now. In 1994, Adleman’s experiment took still a long time to perform. The entire experiment took Adleman 7 days of lab work [13]. Adleman asserts that the time required for an entire computation should grow linearly with the size of the graph. This is true as long as the creation of each edge does not require a separate process.
Practical experiments proved that when people using DNA to solve more complex problems such like SAT problems, more and more laborious separation and detection steps are required, which will only increase as the scale increases. But these problems may be overcomed by using autonomous methods for DNA computation, which execute multiple steps of computation without outside intervention. Actually, autonomous DNA computations were first experimentally demonstrated by Hagiya et al. [14] using techniques similar to the primer extension steps of PCR and by Reif, Seeman et al. [15] using the self-assembly of DNA nanostructures [16]. Recently, Shapiro et al. reported the use of restriction enzymes and ligase [2] on the Nature (Figure 5). They demonstrated a realization of a programmable finite automaton comprising DNA and DNA-manipulating enzymes that solves computational problems autonomously. In their implementation, 1012 automata sharing the same software run independently and in parallel on inputs (which could, in principle, be distinct) in 120 micro liters solution at room temperature at a combined rate of 109 transitions per second with a transition fidelity greater than 99.8%. Thus, the laborious processes can be reduced largely. We can forecast that this problem can be settled very well in not long time.

2) Hydrolysis:
The DNA molecules can fracture. Over the six months you're computing, your DNA system is gradually turning to water. DNA molecules can break – meaning a DNA molecule, which was part of your computer, is fracture by time. DNA can deteriorate. As time goes by, your DNA computer may start to dissolve. DNA can get damaged as it waits around in solutions and the manipulations of DNA are prone to error. Some interesting studies have been done on the reusability of genetic material in more experiments, a result is that it is not an easy task recovering DNA and utilizing it again.

3) Information Untransmittable:
The model of the DNA computer is concerned as a highly parallel computer, with each DNA molecule acting as a separate process. In a standard multiprocessor connection-buses transmit information from one processor to the next. But the problem of transmitting information from one molecule to another in a DNA computer has not yet to be solved. Current DNA algorithms compute successfully without passing any information, but this limits their flexibility.

4) Reliability Problems:
Errors in DNA Computers happen due to many factors. In 1995, Kaplan et al. [17] set out to replicate Adleman’s original experiment, and failed. Or to be more accurate, they state, “At this time, we have carried out every step of Adleman’s experiment, but we have not got an unambiguous final result.” There are a variety of errors that can come along with experimentation. Typical errors are annealing errors, errors in PCR, errors during affinity separation (Purification).