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Understanding Transcription and RNA

Sep 6, 2024

Lecture on Chapter 21: Transcription and RNA

Introduction

  • Focus on RNA structure compared to DNA.
  • Define a gene.
  • Overview of replication, transcription, and translation.

Polymer Formation

  • Processes: Initiation, Elongation, Termination.
    • Initiation: Binding of molecular machine to template.
      • Replication: DNA polymerase.
      • Transcription: RNA polymerase.
      • Translation: Ribosome.
    • Elongation: Reading template, adding next monomer.
      • Replication: Synthesizing DNA.
      • Transcription: Making RNA.
      • Translation: Forming protein.
    • Termination: Release of molecular machine and product.

Definitions

  • Replication: Duplication of DNA.
  • Transcription: Copying DNA into RNA (same nucleic acid language).
  • Translation: Converting nucleic acid language into amino acid language (protein).

Differences between RNA and DNA

  1. Sugar Component
    • DNA: Deoxyribose sugar.
    • RNA: Ribose sugar with a hydroxyl group at the 2' position.
      • Prevents formation of B-type helices in RNA.
  2. Nitrogenous Bases
    • Common: Adenine, Guanine, Cytosine.
    • Difference: Thymine in DNA vs. Uracil in RNA.
      • Thymine has a methyl group; uracil has a hydrogen.

Definition of a Gene

  • Involves generating mRNA, which translates into amino acids.
  • Types of RNA:
    • mRNA: Messenger RNA; translated into protein.
    • rRNA: Ribosomal RNA; not translated.
    • tRNA: Transfer RNA; not translated.

mRNA in Prokaryotes vs. Eukaryotes

  • Prokaryotic mRNA can be polycistronic (multiple genes per mRNA).
  • Eukaryotic mRNA mostly monocistronic but can have overlapping sequences.

Control Elements in DNA

  • Elements like promoters control transcription but aren't transcribed.
  • RNA processing includes splicing introns out of mRNA in eukaryotes.

Types of Genes

  1. Protein-Coding Genes: DNA transcribed to RNA and translated into protein.
  2. Non-Coding RNAs: RNA is transcribed but not translated.
    • 80% of human genome transcription results in non-coding RNAs.

Non-Coding RNA Examples

  • Many types, not necessary to memorize each but know the majority of genes are non-coding.

Next Steps

  • Next lesson: Overview of transcription and chromatin structure.

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