RNA interference (RNAI) is a mechanism of gene regulation in eukaryotes. RNAI is initiated by , which leads to the of specific genes. Box 1:
single-stranded RNA
double-stranded RNA
double-stranded DNA
Box 2:
silencing
induction
expression

double-stranded RNA;  silencing

Explanation:

The RNAi mechanism is a natural process of gene silencing triggered by different small non-coding RNAs such as, for example, siRNAs, miRNAs and piRNAs. RNAi is a powerful technique to induce gene silencing in a sequence-specific manner. The delivery of exogenous double-stranded RNAs (dsRNAs) can be used to induce this evolutionarily conserved mechanism.  The dsRNAs first bind to RNAi core components (Ago, Piwi proteins) and then target complementary mRNAs to induce their degradation.

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.