Correct me if I am wrong, but it seems that if your target is to collect 100 rare DNA, you have to collect rare DNA. You can’t collect 100 epic DNA instead.
If think it would be cool if the goals would overlap like this:
Collect rare covers normal and rare dna.
Collect epic covers normal, rare and epic dna.
Might only be a small change, but would make it a bit more convenient.