Protein Synthesis

Location: Occurs mainly in the nucleus of eukaryotic cells; in prokaryotes, it occurs in the cytoplasm.
Process:
- RNA polymerase unwinds the DNA helix to expose the nucleotide bases of the gene.
- Free RNA nucleotides (A, U, C, G) pair with the exposed DNA template strand using complementary base pairing (A with U, C with G).
- RNA polymerase catalyzes the bonding of RNA nucleotides, forming a single strand of mRNA.
- Introns (non-coding regions) are removed through RNA splicing, while exons (coding regions) are retained and joined together.
- The mature mRNA molecule exits the nucleus through nuclear pores into the cytoplasm.

Location: Takes place in the cytoplasm at ribosomes, which can be free-floating or attached to the endoplasmic reticulum.
Process:
- The mRNA binds to a ribosome, where its codons are read.
- Transfer RNA (tRNA) molecules arrive at the ribosome, carrying specific amino acids. Each tRNA has an anticodon that is complementary to the corresponding mRNA codon.
- Initiation: The ribosome identifies the start codon (AUG), marking the beginning of the polypeptide chain synthesis.
- Chain Elongation: Each tRNA delivers its amino acid, which is added to the growing polypeptide chain via peptide bonds. The ribosome moves along the mRNA, reading each codon in succession.
- Termination: When a stop codon (UAG, UAA, or UGA) is reached, the process concludes. The completed polypeptide chain is released for folding into its final protein structure.

Transcription converts DNA into mRNA in the nucleus, while translation decodes that mRNA into a polypeptide chain in the cytoplasm. Together, these processes are crucial for gene expression and the synthesis of proteins, which perform essential functions in living organisms.