Answer
     The blank is filled with RNA
Explanation
     As we know that there are three types of RNA responsible for protein synthesis.
1. mRNA
       It is that type of RNA which is the exact copy of DNA template and contain the code copied from DNA for required protein.
2. rRNA
      This RNA play a key role in the formation of ribosomes, a smaller organelle inside cell responsible for holding mRNA during protein synthesis.
3. tRNA
      This RNA transport amino acids to the strand of mRNA and help in translation.
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