Proposing 5-Steps Rule Is a Notable Milestone for Studying Molecular Biology

In this current minireview, the cradle of the “5-steps rule” or “5-step rules”, along with its essence and advances, has been recalled. Born in 2011, its impacts on molecular biology are both substantial and rapid, fully indicating the “5-steps rule” is no double a remarkable and profound milestone in molecular biology.


INTRODUCTION
Since it was proposed in 2011, the "5-steps rule" or "5-step rules" has been widely used in molecular biology, both theoretical and experimental. Its original source was usually referred by citing a review paper for celebrating the 50 th anniversary year of Journal of Theoretical Biology [1].
Interestingly, no such a clear-cut term as "5-step" can be found in the entire aforementioned paper. Why? This is because: it is the idea of the "5-steps rule" that would become crystal clear after carefully reading through the whole paper. Accordingly, the paper [1] is actually the cradle of the "5-steps rule".

THE ESSENCE OF 5-STEPS RULE
In order to quantitatively predict, or develop a useful predictor for, a molecular biology system, the following five guidelines should be observed: 1) select or construct a valid benchmark dataset to train and test the predictor; 2) represent the samples with an effective formulation that can truly reflect their intrinsic correlation with the target to be predicted; 3) introduce or develop a powerful algorithm to conduct the prediction; 4) properly perform cross-validation tests to objectively evaluate the anticipated prediction accuracy; 5) establish a user-friendly web-server for the predictor that is accessible to the public. The predictors established in compliance with these steps have the following notable merits: a) crystal clear in logic development; b) completely transparent in operation; c) easily to repeat the reported results by other investigators; d) with high potential in stimulating other predictors; e) very convenient to be used by the majority of experimental scientists.
It is instructive to point out that in the systems of molecular biology there exist many multi-label ones where each of the individual constituents or samples considered may need two or more labels for distinction. For this kind of multi-label systems, two kinds of metrics are needed: one is the global set of metrics to indicate the global accuracy of the prediction method or predictor developed, while the other is the local metrics to indicate its local accuracy [35]. For the concrete mathematical formulations of the two sets of metrics, as well as their biological implications, refer to a recent paper [36].

CONCLUSION AND PERSPECTIVE
The "5-steps rule" has played substantial roles in stimulating in-depth studies of molecular biology, both theoretical and experimental. It is indeed a remarkable and profound milestone for molecular biology.
Although at the present the reports in this regard from theoretical scientists are more than those from experimental scientists, it is anticipated that, with more experimental data available in future, this kind of reports from experimental scientists will be increasing as well. Particularly, the combined reports between experimental and theoretical approaches, or their compliments to each other, will increasingly appear.

CONFLICTS OF INTEREST
The author declares no conflicts of interest regarding the publication of this paper.