A cat thinks that you are opening a can of cat food when it hears the can opener. 
A dog shying away from a magazine or newspaper, if the owner has used one to swat the dog as punishment. 
If humans are ok to use as examples, A child learning that a stove is hot by touching it. 
        
             
        
        
        
Answer:
- Duplex RNA (dsRNA) can suppress the expression of a gene.
- miRNAs are short, single strands approximately 21 nucleotides long.  
- miRNAs suppress gene expression by interfering with transcription.  
- RNA interference can temporarily suppress the expression of a target gene.
Explanation:
The RNA interference (RNAi) mechanism is a naturally occurring biological process by which an organism suppresses gene expression by using sequence-specific small non-coding RNAs that are complementary to RNA (posttranscriptional silencing) or DNA (transcriptional silencing) sequences. Since its discovery, this mechanism has been exploited in molecular biology to control the expression of target genes. There are different classes of non-coding RNAs which are able to trigger RNAi gene silencing: microRNAs (miRNAs), small interfering RNAs (siRNAs), piwi-interacting RNAs (piRNAs, only present in animals), etc. During their functioning, these non-coding RNAs are loaded into the RNA-induced silencing complex (RISC) to direct them to target sequences and trigger RNAi (for example, by cleaving target mRNAs). miRNAs are short, evolutionary conserved RNAs, that associate to the RISC complex in order to trigger both transcriptional and posttranscriptional gene silencing. During their biogenesis, small non-coding RNAs are double-stranded RNA (dsRNA), but they lose a strand (the passenger strand) when associate with the RISC complex, conserving only one strand (the guide strand) that bind by complementary base pairing to target sequences (either DNA in the nucleus or RNA in the cytoplasm).
 
        
             
        
        
        
Answer: 
 A purulent wound produces fluid which are releases from the purulent wound. Basically, it is the type of the fluid which are produced in the form of milky type and it is the symptoms of the infection in the body. It is also known as purulent drainage, which are basically the sign of infection in the wound or hole in the skin of our body and then it needs proper treatment.