Molecular tools are essential for diverse applications in genetics and public health.
The Polymerase Chain Reaction (PCR) is a widely known molecular tool, particularly used during the COVID-19 pandemic for testing.
The focus of this discussion is on CRISPR as a significant tool for genome or genetic engineering.
Central Dogma of Molecular Biology
Understanding the central dogma is critical since the processes involved can be harnessed to develop various molecular tools.
Examples of applications derived from the central dogma include:
Genetic Engineering
Gene Expression Control
Turning genes on/off
Analyzing gene expression effects in diseases (e.g., cancer)
Diagnosis, Prognosis, & Treatment Outcomes
Sequencing Genomes
The evolution and engineering of molecules allow for accurate high-throughput genome sequencing.
mRNA Vaccines during COVID
mRNA vaccines were produced using RNA polymerases and purified DNA to generate worldwide supplies of mRNA for vaccination.
This represents an impactful application of molecular tools in manufacturing.
Genome Engineering Focus
Definition of Genome Engineering
The goal is to make precise changes to the genetic material of an organism to correct mutations causing diseases.
Example Case: A mutation in human DNA leads to a faulty messenger RNA and then to a dysfunctional protein, which may cause disease.
The modification aims to correct the original mutation so that the resultant protein functions normally.
CRISPR-Cas9 Tool Development
Introduced as a tool effective for genetic modifications within the last decade.
Background to CRISPR-Cas9
CRISPR research originally stemmed from microbiologists and genome sequencing scientists.
Initial Discoveries:
Observations were made on bacteria's defenses against bacteriophages (viral infections of bacteria) resulting in interest from yogurt makers.
Genome sequencing efforts revealed repetitive sequences (CRISPR) associated with Cas genes found in bacterial chromosomes.
These assist bacteria in protecting against infections by storing sequences from previous phage attacks.
Mechanism of CRISPR-Cas System
Bacterial Defense Mechanism
The CRISPR locus transcribes RNA molecules that form a structure capable of recognizing and cleaving the DNA of invading plasmids (bacteriophages).
The guide RNAs (gRNAs) play a critical role in this recognition by pairing with the DNA.
Understood Functions
When introducing CRISPR-Cas9 into genetic modification applications, the potential of directing cuts at any DNA target was realized, expanding beyond bacteriophages.
Engineering CRISPR-Cas9 for Biotechnology
Application to Gene Editing
The Cas9 protein can use guide RNAs to create double-strand breaks in desired DNA sequences.
The cell's repair systems engage, repairing the break through two main pathways:
Non-Homologous End Joining (NHEJ)
Can introduce insertions or deletions, creating gene knockouts.
Homologous Recombination (HR)
Allows for precise editing by supplying a donor sequence that is integrated at the cut site.
Nobel Prize Achievement
Emmanuel Charpentier and Jennifer Doudna won the Nobel Prize in Chemistry in 2020 for their discoveries leading to CRISPR-Cas9's applicability in genetic engineering.
Structural Studies of CRISPR-Cas9
CRISPR-Cas9 structures have been resolved to understand the protein's mechanics, including guiding RNAs and target DNA interactions.
Importance of Motility:
Motions of Cas9 are critical for its functionality, ensuring precise cuts at targeted DNA sequences.
Fidelity Studies:
Investigations into how mutations impact the accuracy of Cas9 action provide insights into making CRISPR technology more precise.
Current Applications and Future Directions
Uses of CRISPR Technology
Engineering animal models for human diseases (e.g., mice with cancer models).
Generating crops resistant to stressors like drought and pests.
Targeting genetic diseases for treatment, with sickle cell disease as a notable example.
Sickle Cell Disease and Genetic Engineering
The disease results from a single mutation in hemoglobin.
Utilizing CRISPR to correct this mutation in red blood cell precursor cells targets an effective therapeutic pathway.
A successful case involved a patient named Victoria Gray, who underwent CRISPR treatment for sickle cell anemia, marking historic advancements in gene editing therapies.
Challenges and Ethical Considerations
Cost and Duration of Drug Development
Drug development processes can take ten to thirty years, costing around a billion dollars on average.
Comparison of Therapeutic Markets
Successful drug markets (e.g., diabetes medications) contrast with under-invested areas such as new antibiotic discovery, highlighting the funding dilemma in medical research.
Molecular Basis of Cancer
Cancer Development and Process
DNA damage from resources such as radiation, chemicals, and viruses leads to mutations in genes responsible for cell growth and repair.
Tumorigenesis involves oncogenes and tumor suppressor genes, with mutations causing unchecked cell division and failure of cell death mechanisms.
Example of Oncogenes and Tumor Suppressors
Oncogenes: Mutations in genes like RAS lead to excessive cell growth.
Tumor Suppressors: For instance, p53 is a key tumor suppressor whose dysfunction is seen in many cancers, hindering the cell’s ability to regulate itself.
Summary of Cancer Statistics
Data indicates that cancer remains a leading cause of death globally and emphasizes the need for targeted research in therapies.
Emphasis on Research in Cancer Treatment
Understanding molecular mechanisms allows for the design of innovative therapies targeting critical pathways in tumor development.