There are three main types of RNA involved in the the synthesis of proteins:

• Messenger RNA (mRNA) is the transcript copy of the DNA instructions (it encodes the protein sequence) 
  

• Transfer RNA (tRNA) carries the protein subunits (amino acids) to the mRNA transcript
  

• Ribosomal RNA (rRNA) provides the catalytic activity for combining the amino acids according to the mRNA sequence
  

While mRNA is a linear molecule, complementary base pairing can allow tRNA and rRNA to twist and form loops

Types of RNA