Final answer:
Transfer RNA (tRNA) is responsible for bringing new amino acids to the growing protein chain during translation. It pairs specifically with codons on the mRNA to ensure the correct sequence of amino acids is formed in the protein.
Step-by-step explanation:
The type of RNA responsible for bringing new amino acids to the growing protein during protein synthesis is transfer RNA (tRNA). During the translation process, each tRNA molecule carries a specific amino acid to the ribosome.
The mRNA molecule is read by the ribosome in sets of three bases known as codons, each coding for a single amino acid. The tRNA pairs its anticodon with the codon on the mRNA, ensuring the correct amino acids are joined in the proper sequence to form the protein.
The role of tRNA is crucial because it interprets the genetic code from the mRNA and provides the corresponding amino acids to synthesize proteins. Unlike tRNA, ribosomal RNA (rRNA) is a major constituent of ribosomes and helps in the alignment and catalysis of peptide bond formation. MicroRNA (miRNA) is involved in the regulation of gene expression by modulating the activity of mRNA. Hence, the correct answer to the question is 'd. tRNA', as it is the molecule tasked with shuttling amino acids to the growing polypeptide strand.