Which of the following RNA’s should be most abundant in an animal cell?

(a) miRNA

(b) tRNA

(c) mRNA

(d) rRNA

There are three main types of RNA: rRNA, mRNA, and tRNA.

• rRNA (ribosomal RNA) is the most abundant form of RNA and plays a crucial role in protein synthesis. It is associated with ribosomes and is responsible for coding.
• mRNA (messenger RNA) provides the template for translation, which is the process by which proteins are synthesized.
• tRNA (transfer RNA) brings amino acids to the ribosome and decodes the genetic code carried by mRNA.

Process of Translation in Protein Synthesis:

• Translation is the process where an mRNA message is decoded into a polypeptide chain, or protein. The mRNA sequence, written in nucleotides, is "translated" into amino acids, the building blocks of proteins.
• Components Needed for Translation:
  • mRNA (from transcription)
  • Ribosomes
  • tRNAs
  • Amino acids
  • Energy sources and various enzymes
• Once mRNA is synthesized, it moves to the cytoplasm where it binds to ribosomes, which are the sites of protein synthesis.
• Ribosomes have three major binding sites:
  1. mRNA binding site
  2. A site (for tRNA)
  3. P site (for tRNA)
• The P site initially holds the codon methionine, and the A site binds to the second codon. A tRNA molecule pairs with the mRNA codon in the A site through complementary base pairing of the tRNA’s anticodon.
• A peptide bond is formed between the amino acid in the A site and the methionine in the P site. The ribosome moves along the mRNA, causing the tRNA to move from the A site to the P site. This continues until a stop codon is encountered.
• Once a stop codon is in the A site, the protein chain is released, and translation is complete.

Thus, the correct answer is ‘rRNA’.