When should I apply the correction to the p-values for multiple testing adjustment?

I was doing a t-test with R in order to check if the means of 2 groups of measurements of the mRNA produced by 5 genes (the two groups are different because of the time in which they have been extracted. One is at 0min from the irradiation and the other one at 120 min from the exposition to gamma radiation) are the same or not. So I wrote a code which reports at the end 5 p-values for each of the 5 genes. Now, details apart, should I apply the correction to the p-values obtained, like the Bonferroni, because of the fact that it has been done many tests (5 tests) and there could be false positives ? I was wondering if 5 tests was a high number so that I must do the multiple testing adjustment.