Understanding Transcription and the Central Dogma

Apr 2, 2025

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Lecture Notes: Transcription and the Central Dogma

Overview of Central Dogma

  • Central Dogma Definition
    • DNA makes RNA, RNA makes protein.
    • Coined by Francis Crick.
    • Original statement: Information flows from nucleic acids to proteins.
    • Misconception: Crick didn't specify DNA to RNA to protein.

Transcription Process

  • Structure of DNA

    • Genome represented as a double helix.
    • Contains genes with start and stop points (5' to 3').

  • Role of Promoter

    • DNA has signals known as promoters.
    • Promoters attract enzymes to start transcription.
    • Transcription direction: 5' to 3'.

  • Transcription Mechanism

    • Enzyme copies DNA to RNA.
    • RNA is synthesized from 5' to 3'.
    • Process called Transcription.

Differences between DNA and RNA

  • Chemical Differences

    • DNA: 2' deoxyribose sugar; RNA: ribose sugar.
    • DNA contains thymine (T); RNA contains uracil (U).
    • Uracil differs from thymine by a methyl group.

  • Structural and Stability Differences

    • RNA is less stable due to ribose sugar.
    • Base pairing differences due to sugar structure.

Transcription Machinery

  • RNA Polymerase

    • Enzyme responsible for synthesizing RNA from DNA.
    • Requires nucleotides with triphosphates.
    • Assisted by other proteins to identify starting points.

  • Directionality and Strands

    • Genes can be transcribed in either direction.
    • RNA polymerase works with the assistance of other proteins.
    • The strand transcribed affects the RNA produced.

Cell-Specific Transcription

  • Gene Regulation
    • Different cell types transcribe different genes.
    • Example: Liver cells vs. muscle cells vs. brain cells.
    • Gene Regulation: How cells decide which genes to transcribe.

Next Steps

  • Future Topics
    • Translation of RNA into protein.
    • Variations of transcription and translation processes.

Note: This lecture covers the basics of transcription and introduces the concept of gene regulation. Upcoming topics will delve into protein synthesis from RNA and explore further complexities in transcription and translation.

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