What is the main role of messenger RNA (mRNA)?

Messenger RNA (mRNA) serves a crucial function in the process of gene expression by carrying genetic information from DNA to ribosomes, where proteins are synthesized. The sequence of nucleotides in mRNA is transcribed from the DNA template, and this sequence encodes the instructions needed for assembling amino acids in the correct order to form proteins.

Once synthesized, mRNA travels from the nucleus to the ribosomes in the cytoplasm, where translation occurs. The ribosomes read the mRNA sequence in sets of three nucleotides (codons), and each codon specifies a particular amino acid. This process is essential for protein synthesis, which is vital for cellular functions and overall organismal development.

The other roles mentioned in the options do not pertain to mRNA. Ribosomal RNA (rRNA) is responsible for forming the structure of ribosomes, while transfer RNA (tRNA) transports amino acids to the ribosome during protein synthesis. DNA replication is a separate process involving enzymes and does not involve mRNA directly. Therefore, the primary responsibility of mRNA is the transport of genetic information from DNA to the ribosomes for protein production.