Lecture Notes: Gene Expression and Gene Technologies

Introduction

• Overview of Topic 8: Gene Expression and Gene Technologies
• Comprehensive coverage of basics as per the specification

Mutation

Gene Mutations

• Changes in DNA base sequence occurring during DNA replication (interphase)
• Mutagenic Agents: Increase mutation frequency (e.g., ionizing radiation)
• Effects:
  • Different amino acid coding, altering protein function
  • Potential for non-functioning proteins
  • Cancer if occurred in cell cycle genes

Types of Gene Mutations

1. Addition: Extra nucleotide added, causing frame shift
2. Deletion: Base removed, causing frame shift
3. Substitution: Base swapped, possibly silent due to genetic code degeneracy
4. Inversion: Base sequence inverted upon rejoining
5. Duplication: Base duplication, causing frame shift
6. Translocation: Bases move to a different chromosome, affecting phenotype

Stem Cells

• Origin: From undifferentiated stem cells

• Types: Totipotent, Pluripotent, Multipotent, Unipotent

  • Totipotent: Any cell type
  • Pluripotent: Most cell types, except placenta
  • Multipotent: Limited cell types (e.g., bone marrow)
  • Unipotent: One cell type

• Ethical Issues: Use of pluripotent stem cells

  • Solution: Induced pluripotent stem cells (iPSCs)

Transcription Factors

• Control transcription in eukaryotes
• Mechanism:
  • Move to nucleus, bind to DNA receptors
  • Switch genes on/off
• Estrogen: Steroid hormone initiating transcription
  • Diffuses into cell, binds to transcription factor receptor

Epigenetics

• Definition: Heritable change in gene function without DNA sequence change
• Mechanisms:
  • Methylation: Inhibits transcription by condensing DNA
  • Acetylation: Influences transcription through histone binding

RNA Interference (RNAi)

• Function: Inhibits translation by destroying mRNA
• Small Interfering RNA (siRNA):
  • Binds to mRNA, cleaving it to inhibit translation

Cancer and Tumor Development

Types of Tumors

• Benign: Non-cancerous, slow growth
• Malignant: Cancerous, rapid growth, metastasize

Genetic Causes

• Oncogenes: Mutated proto-oncogenes causing unregulated cell division
• Tumor Suppressor Genes: Normally inhibit cell division
  • Mutation causes loss of regulation, leading to cancer

Epigenetic Causes

• Methylation: Abnormal methylation can activate/deactivate genes leading to cancer

Estrogen and Cancer

• Mechanism: Post-menopausal estrogen production linked to breast cancer
• Positive Feedback: Tumor growth increases estrogen production

Genome and Sequencing

• Genome Definition: Complete genetic material
• Sequencing Advancements: Automated and continuously improving methods

Gene Technologies

Recombinant DNA Technology

• Purpose: Manipulate genes for industrial or medical use (e.g., insulin production)
• Methods of DNA Fragment Creation:
  1. Reverse Transcription
  2. Restriction Endonucleases
  3. Gene Machine

DNA Cloning (In Vivo and In Vitro)

• In Vivo Cloning: Using vectors like plasmids, modifying DNA fragments
• Gene Markers: Identify successful DNA insertion
• In Vitro Cloning (PCR): Rapid, automated amplification of DNA fragments

DNA Probes and Applications

• DNA Probes: Locate specific alleles using labeled DNA
• Applications: Screening for genetic conditions, personalized medicine

Genetic Fingerprinting

• VNTRs: Used to identify genetic relationships and variability
• Applications: Forensic science, paternity testing, medical diagnosis

Conclusion

• Summary of the importance and applications of gene expression and gene technologies in biology