Final answer:
Francis Crick proposed the existence of transfer RNA (tRNA) as small adaptor RNA molecules that would act as decoders carrying their own amino acids and interacting with the messenger RNA (mRNA) template in a position for polymerization to take place.
Step-by-step explanation:
Francis Crick proposed the existence of small adaptor RNA molecules that would act as decoders carrying their own amino acids and interacting with the messenger RNA (mRNA) template in a position for polymerization to take place. These adaptors are known as transfer RNA (tRNA).