Stuttering is a speech disorder characterized by repetition of sounds, syllables, or words; prolongation of sounds; and interruptions in speech known as blocks. An individual who stutters exactly knows what he or she would like to say but has trouble producing a normal flow of speech.
The 3 types of RNA are mRNA is a long strand, the tRNA is shaped  like a clover leaf pattern. The third shape is Ribosomal RNA, it  is a very complex shape.
There are three types of RNA: mRNA (messenger RNA), rRNA (ribosomal RNA) and tRNA (transfer RNA). As far as DNA is concerned, there is only one type of DNA. ;) Another difference. Also, in some viruses the RNA replaces the DNA but the DNA will never replace the RNA.