IS

MODULE 2: LECTURE 4 NOTES

Overview of CRISPR and Genetic Disorders

  • CRISPR Technology: Powerful genetic tool used for editing DNA to correct genetic disorders.

  • Cystic Fibrosis Award: Recently awarded scientists for advancements in understanding and treating cystic fibrosis through genetic editing.

Impact of Metabolic Disorders

  • Case Study: Highlights a specific child's struggle with a metabolic disorder caused by excess ammonia due to a genetic mutation.

  • Consequences: Significant organ damage affecting the brain, intestine, and liver can result from elevated ammonia levels, potentially leading to death.

  • CRISPR-Cas9 Therapy: Developed to address the genetic mutation rapidly and effectively in the child, transitioning CRISPR from laboratory research to clinical application.

  • Virus Mutation Concerns: Possible rapid mutation of viruses when using genetic editing tools in organisms could lead to increased spread of diseases.

Genetic Material and Transcription

Historical Context

  • RNA as Information Carrier: Historically, RNA was thought to be the primary genetic and information source.

  • Messenger RNA (mRNA): Serves as a template for protein synthesis.

Transcription Process

  • Comparison of Prokaryotes and Eukaryotes:

    • Prokaryotes: Transcription and translation occur in the same cellular compartment without organelles.

    • Eukaryotes: These processes are compartmentalized; transcription occurs in the nucleus, and translation occurs in the cytoplasm.

RNA Synthesis Nomenclature

  • Directionality of RNA: RNA is synthesized in a 5' to 3' direction, reflecting sequence order and allowing for proper complementary strand pairing.

  • Template Strand Identification: Students should determine which DNA strand serves as the template for RNA synthesis based on transcription directionality.

Complementary Strand Nomenclature

  • Template Strand vs Non-template Strand:

    • The non-template strand (coding strand) has thymine (T) while the RNA transcript uses uracil (U).

    • Noticeable similarity between the RNA strand and the non-template strand except for T (in DNA) and U (in RNA).

Transcription Initiation Complexity

Gene Structure

  • Transcribed Regions:

    • Genes can be coded on either strand of a double-stranded DNA molecule. For example, genes A and B may transcribe in opposite directions.

Promoter Sequences

  • Definition: Specific DNA sequences that signal the start of transcription.

  • TATA Box: A conserved sequence in many promoters that is crucial for initiating transcription, usually located about 25 base pairs upstream of the transcription start site.

  • Transcription Factors: Bind to promoter sequences and facilitate the recruitment of RNA polymerase.

Enhancers and Silencers

  • Definition of Enhancer Sequences: DNA elements that enhance transcription efficiency, can be located at various distances from the promoter.

  • Binding of Transcriptional Activators: Activators bind to enhancers to enhance the transcription process; a complex interaction occurs between different proteins and DNA sequences to start transcription.

Transcription Complex Formation

Assembly of Transcription Complex

  • Role of TBP (TATA Box Binding Protein):

    • Recognizes TATA box and recruits general transcription factors to form a transcription complex.

  • Mediator Role: Connects transcriptional activators to the transcription machinery at the promoter, facilitating RNA polymerase recruitment.

Elongation Phase

  • Initiation to Elongation Transition: Following initiation of transcription, the elongation phase begins, in which RNA polymerase synthesizes RNA using the DNA template strand.

  • Directionality During Elongation: Continues in a 5' to 3' direction; building RNA transcript in the proper sequence based on the template strand.