Molecular Biology: Gene Expression & RNA

1. 📌 Essentials

• Transcription: DNA to RNA synthesis by RNA polymerase.
• RNA processing: Capping, polyadenylation, splicing (removal of introns).
• Translation: mRNA decoding into amino acid chains by ribosomes.
• Promoter sequences: Bacterial (-10, -35); Eukaryotic (TATA box).
• RNA types: mRNA, tRNA, rRNA, snRNA, regulatory RNAs.
• Genetic code: 64 codons, AUG start, UAA/UAG/UGA stop.
• RNA modifications: 5′ cap, 3′ poly-A tail, sp.
• RNA's catalytic role: Ribozymes, self-replication- Gene structure: Exons (coding), introns (noncoding).
• Key differences: Prokaryotic vs eukaryotic transcription and processing.

2. 🧩 Key Structures & Components

• RNA polymerase — enzyme synthesizing RNA from DNA template.
• Promoters — DNA sequences signaling initiation (-10, -35 in bacteria; TATA in eukaryotes).
• snRNPs — small nuclear ribonucleoproteins involved in splicing.
• Ribosome — molecular machine translating mRNA; has A, P, E sites.
• tRNA — adaptor molecules matching codons to amino acids.
• mRNA — messenger RNA carrying genetic info.
• Spliceosome — complex of snRNPs executing splicing.
• Ubiquitin-proteasome system — degrades proteins tagged with ubiquitin.
• RNA modifications — 5′ cap, 3′ poly-A tail, exon junction complexes.
• Genetic code — codon table translating nucleotide triplets into amino acids.

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