explain that genetic engineering is the deliberate manipulation of genetic material to modify specific characteristics of an organism and that this may involve transferring a gene into an organism so that the gene is expressed

Principles of Genetic Technology

Learning Objective

Explain that genetic engineering is the deliberate manipulation of genetic material to modify specific characteristics of an organism and that this may involve transferring a gene into an organism so that the gene is expressed.

Key Definitions

• Genetic engineering (genetic modification): The intentional alteration of an organism’s DNA to achieve a desired trait.
• Gene: A segment of DNA that encodes a functional product, usually a protein.
• Vector: A DNA molecule (e.g., plasmid, virus) used to carry a foreign gene into a host cell.
• Host organism: The cell or organism that receives the recombinant DNA and expresses the introduced gene.
• Expression: The process by which a gene’s information is used to synthesize a functional product.

Steps in a Typical Genetic Engineering Procedure

1. Isolation of the gene of interest

   DNA is extracted from the donor organism and the target gene is cut out using restriction enzymes.

2. Insertion into a vector

   The gene fragment is ligated into a plasmid or viral vector that contains selectable markers.

3. Introduction of the recombinant vector into a host cell

   Methods include transformation (bacteria), transfection (eukaryotic cells), or infection (viral vectors).

4. Selection of successfully modified cells

   Cells that have taken up the vector are identified using antibiotic resistance or reporter genes.

5. Expression and verification

   The host cell’s machinery transcribes and translates the introduced gene; expression is confirmed by assays such as PCR, gel electrophoresis, or protein activity tests.

Common Tools and Techniques

• Restriction enzymes – cut DNA at specific sequences.
• DNA ligase – joins DNA fragments.
• Polymerase chain reaction (PCR) – amplifies the gene of interest.
• Plasmid vectors – circular DNA molecules used in bacterial cloning.
• Viral vectors – adenovirus, lentivirus, used for eukaryotic cells.
• CRISPR‑Cas9 – precise genome editing by creating double‑strand breaks at target sites.

Methods of Gene Transfer

Expression of the Transferred Gene

For a transferred gene to be functional, it must be transcribed and translated in the host. This requires:

• A promoter compatible with the host’s transcription machinery.
• Proper ribosome binding sites (in prokaryotes) or Kozak sequence (in eukaryotes).
• Absence of premature stop codons or intron‑exon incompatibilities.

Applications of Genetic Engineering

• Production of insulin, growth hormone, and other therapeutic proteins.
• Genetically modified crops with pest resistance, herbicide tolerance, or enhanced nutrition.
• Gene therapy for inherited diseases.
• Creation of model organisms (e.g., knockout mice) for research.

Ethical and Safety Considerations

While genetic engineering offers many benefits, it raises questions about:

• Potential ecological impacts of releasing GM organisms.
• Gene flow to wild relatives.
• Human health risks from unintended effects.
• Socio‑economic issues such as patenting of life forms.