Key Enzymes in DNA Replication, Transcription, and Translation

Helicase

Unwinds the DNA helix at the replication fork.

Topoisomerase (DNA Gyrase)

Relieves the tension ahead of the replication fork by cutting and rejoining DNA strands.

Single-Stranded Binding Proteins (SSBs)

Stabilize single-stranded DNA to prevent it from re-annealing.

Primase

Synthesizes a short RNA primer to provide a starting point for DNA synthesis.

DNA Polymerase III

Main enzyme responsible for adding nucleotides to the growing DNA strand in a 5' to 3' direction during replication.

DNA Polymerase I

Removes the RNA primer and replaces it with DNA.

Ligase

Seals the gaps between Okazaki fragments on the lagging strand, forming a continuous DNA strand.

RNA Polymerase

Synthesizes RNA from a DNA template during transcription.

RNA Polymerase I

Transcribes rRNA.

RNA Polymerase II

Transcribes mRNA.

RNA Polymerase III

Transcribes tRNA and other small RNAs.

Capping Enzymes

Add a 5' cap to mRNA to protect it from degradation.

Poly(A) Polymerase

Adds a poly-A tail to the 3' end of mRNA for stability and regulation of export from the nucleus.

Spliceosome

Responsible for removing introns from pre-mRNA during RNA splicing.

Aminoacyl-tRNA Synthetase

Attaches the appropriate amino acid to its corresponding tRNA.

Ribosome

The molecular machine that facilitates the decoding of mRNA into a polypeptide chain (protein).

Large Subunit (60S)

Where peptide bond formation occurs.

Small Subunit (40S)

Binds to the mRNA and ensures proper codon-anticodon pairing.

Peptidyl Transferase

Catalyzes the formation of peptide bonds between amino acids during translation.