Do you think humans will be able to genetically engineer future humans in your life time?
do you think humans should be engineering human dna?
are there some events when we should? when we should not?

Yes, they could, but they shouldn't because there can be many mistakes. There are some such as if we want someone to be immune to some diseases. But we shouldn't if it's a situation that we want someone more beautiful!

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

on island x the species needed to adapt because they were being subject to predators which didn't inhabit island y.