Amoeba Sisters Video Recap: DNA vs. RNA & Protein Synthesis UPDATED Protein Synthesis Summary
The Correct Answer and Explanation is :
Correct Answer:
Protein Synthesis Summary
Protein synthesis involves two main stages: transcription and translation.
- Transcription occurs in the nucleus, where the DNA sequence of a gene is used to synthesize messenger RNA (mRNA). RNA polymerase unzips the DNA and assembles the mRNA strand based on complementary base pairing (A pairs with U, and C pairs with G in RNA). Once formed, the mRNA exits the nucleus.
- Translation occurs in the cytoplasm at the ribosome. Here, the mRNA sequence is read in codons (groups of three bases). Transfer RNA (tRNA) brings specific amino acids to the ribosome. Each tRNA has an anticodon that pairs with a complementary mRNA codon, ensuring the correct amino acid sequence. The amino acids are linked together to form a polypeptide chain, which folds into a functional protein.
Explanation (300 words):
Protein synthesis is a crucial biological process that converts genetic instructions stored in DNA into functional proteins. This process involves two stages: transcription and translation.
Transcription occurs in the cell nucleus. Here, an enzyme called RNA polymerase binds to the DNA at the gene’s promoter region. The DNA unwinds, and RNA polymerase synthesizes a single-stranded mRNA molecule complementary to the DNA template. In RNA, the base uracil (U) replaces thymine (T), so adenine (A) pairs with uracil during transcription. After transcription, the mRNA undergoes modifications like splicing, where introns (non-coding regions) are removed, and a 5’ cap and poly-A tail are added for stability. The mature mRNA exits the nucleus through nuclear pores.
Translation takes place in the cytoplasm, where ribosomes facilitate the decoding of mRNA into a protein. The ribosome reads the mRNA codons, and each codon corresponds to a specific amino acid. Transfer RNA (tRNA) molecules, with their anticodons, deliver the correct amino acids. For example, the mRNA codon AUG (start codon) codes for methionine, initiating the process. The ribosome links amino acids via peptide bonds, creating a growing polypeptide chain. This process continues until the ribosome encounters a stop codon (UAA, UAG, or UGA), signaling the release of the completed protein.
The synthesized protein then folds into its specific 3D shape, which determines its function. This intricate process highlights the role of DNA, RNA, and ribosomes in gene expression and the central dogma of molecular biology.