Human Biology · MU Plovdiv

6. Transcription. Necessary elements, stages and mechanism. Reverse transcription.

Inside: 40 sections · 5 labelled pictures · 7 tables · 46 flashcards · 18 min

Topic 6 of 66 in the MU Plovdiv syllabus for Human Biology (Medicine, Year 1). The free AceMed note covers it in 39 sections, about 2,128 words (18 min of reading), with 46 flashcards.

In this note

  1. Transcription:
  2. Definition
  3. General Characteristics
  4. Enzymes Involved
  5. Energy in Transcription
  6. Stages of Transcription
  7. Transcription Unit
  8. Prokaryotic Transcription
  9. Eukaryotic Transcription
  10. Clinical Note: Death Cap Mushroom
  11. Mnemonics
  12. RNA replication. Reverse transcription
  13. Viral Genomes and the Baltimore Classification
  14. RNA Replication – RNA-dependent RNA replication
  15. Different RNA Viruses, Different Strategies
  16. Reverse Transcription – RNA to DNA
  17. HIV: A Closer Look at Reverse Transcription
  18. Error-Prone but Advantageous
  19. Targeting Viral Enzymes with Drugs
  20. Updating the Central Dogma
  21. 💣 HIV Process Mnemonic: “tRAP-jump-PPT”
  22. 6 🧬 RNA Processing Cheat Sheet
  23. 🧬 Genetic Code & Translation — Cheat Sheet
  24. 7 🔧 Translation: Making Proteins from mRNA
  25. 🔐 Translation Regulation
  26. 🧬 Proteins After Translation — Cheat Sheet
  27. 🧬 DNA Replication — Cheat Sheet
  28. ⚙ Phases of Replication
  29. 2⃣ Elongation
  30. 3⃣ Termination
  31. 🔁 Modes of Replication
  32. 🔑 Key Enzymes
  33. 🧬 Chromatin & Telomeres
  34. 🧬 RNA Replication & Reverse Transcription — Cheat Sheet
  35. 🧬 3. Reverse Transcription – RNA to DNA
  36. 🧪 4. HIV Example of Reverse Transcription
  37. ⚠ 5. RT is Error-Prone
  38. 💊 6. Antiviral Drug Targets
  39. 🧬 7. Updated Central Dogma

Definition

Transcription is the process by which RNA is synthesized using a DNA segment as a template.

General Characteristics

  • DNA stores genetic information.
  • Genes are expressed via transcription into RNA.
  • RNA is synthesized from the 5' to 3' direction.
  • RNA and DNA strands are antiparallel and complementary.
  • Specific promoter and terminator sequences define start and end.

Enzymes Involved

DNA-dependent RNA Polymerase:

  • Separates DNA strands temporarily.
  • Uses one DNA strand as a template.
  • Catalyzes phosphodiester bond formation.
  • Involved in gene regulation.

Structure: Complex quaternary protein.

Energy in Transcription

  • Ribonucleotides (ATP, UTP, GTP, CTP) provide energy.
  • Energy released from phosphate bond cleavage.
  • Pyrophosphate hydrolyzed by pyrophosphatase, pushing reaction forward.

Stages of Transcription

1. Initiation

  • Transcription factors bind TATA box (promoter).
  • RNA Polymerase forms the transcription initiation complex.
  • DNA unwinds, and phosphodiester bonds begin forming.

2. Elongation

  • RNA Polymerase adds complementary nucleotides to the 3' end of RNA.
  • DNA helix reforms after polymerase passes.
  • Topoisomerases relieve supercoiling.

3. Termination

  • RNA Polymerase halts at terminator sequence.
  • Transcript is released.

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