Learning Objective: By the end of this lesson, the learner should be able to describe the major types of RNA, their functions, cellular locations, and their roles in gene expression and protein synthesis.

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Activity

RNA molecules perform diverse functional and structural roles that are essential for gene expression, protein synthesis, and regulation. Below are the major classes of RNA.

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Ribosomal RNA (rRNA)

• Most abundant RNA type in the cell.
• Combines with ribosomal proteins to form the ribosome.
• Provides both structural integrity and catalytic activity (peptidyl transferase).

Key Features

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Transfer RNA (tRNA)

• The second most abundant RNA type.
• Each tRNA carries a specific amino acid to the ribosome.
• Contains an anticodon complementary to mRNA codons.

Key Features

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Messenger RNA (mRNA)

• Carries genetic information from DNA to ribosomes.
• Only RNA type that is translated.
• Highly heterogeneous in size and sequence.

Key Features

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Heterogeneous Nuclear RNA (hnRNA / pre-mRNA)

• Found only in eukaryotic nuclei.
• Primary transcript made during transcription.
• Undergoes capping, polyadenylation, and splicing to become mature mRNA.

Key Features

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Small Nuclear RNA (snRNA)

• Exclusively nuclear.
• A major component of the spliceosome.
• Responsible for the removal of introns from pre-mRNA.

Key Features

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Ribozymes

• RNA molecules with enzymatic activity.
• Found in both prokaryotes and eukaryotes.
• It can catalyze reactions such as self-splicing, RNA cleavage, and peptide bond formation.

Key Features

Activity

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Summary Table

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Activity