Unit 2: Medicine and Healthcare Biotechnology

Introduction to Genetic Engineering

Genetic Engineering, also known as recombinant DNA (rDNA) technology, is the direct manipulation of an organism's genes. It involves isolating a specific gene and inserting it into another organism (often a bacterium) to produce a desired product.

Basic Steps of Genetic Engineering:

1. Gene Isolation: The desired gene (e.g., the human insulin gene) is cut out of the source DNA using restriction enzymes (molecular scissors).
2. Vector Insertion: The gene is "pasted" into a vector, which is a DNA molecule used to carry the gene into a host. A common vector is a plasmid (a small, circular piece of DNA from a bacterium).
3. Transformation: The recombinant vector (plasmid) is introduced into a host cell (like the bacterium E. coli).
4. Cloning & Selection: The host cell divides, creating millions of copies ("clones") of itself, all containing the recombinant plasmid.
5. Expression: The host cells "express" the new gene, meaning they follow its instructions to produce the desired protein (e.g., human insulin).

Production of Therapeutic Products

Insulin

• Function: A hormone that regulates blood sugar. Diabetics cannot produce it.
• Old Method: Insulin was extracted from the pancreases of pigs and cows. This was expensive, inefficient, and caused allergic reactions.
• Biotech Method: The human insulin gene was inserted into *E. coli* bacteria. These bacteria act as fast-growing "factories" that produce large quantities of pure, safe, and affordable "Humulin" (Human Insulin).

Growth Hormone

• Function: A hormone essential for normal growth. Lack of it causes pituitary dwarfism.
• Old Method: Used to be extracted from the pituitary glands of human cadavers. This was extremely rare and carried a high risk of transmitting diseases.
• Biotech Method: The human growth hormone gene was cloned into bacteria, providing a safe, unlimited, and ethical supply.

Gene Therapy

Definition: Gene Therapy

A medical technique that aims to treat or cure genetic diseases by introducing a "correct" or functional gene into a patient's cells to replace or repair a faulty gene.

• Potential: It offers the hope of a one-time cure for inherited disorders like cystic fibrosis, hemophilia, muscular dystrophy, and sickle cell anemia.
• Mechanism:
  1. A functional copy of the gene is packaged into a vector (often a modified, harmless virus like an adenovirus).
  2. The vector "infects" the target cells (e.g., lung cells for cystic fibrosis).
  3. The vector delivers the functional gene into the cell's nucleus.
  4. The cell begins to use the new gene to produce the correct protein.
• Challenges: Ensuring the gene is delivered to the right cells, avoiding an immune response to the vector, and controlling where the gene inserts into the host's DNA are all major hurdles.

Forensic Science

Forensic science uses biotechnology, specifically DNA fingerprinting, to identify individuals with incredible accuracy.

Solving Violent Crimes & Paternity

• Violent Crimes (Murder/Rape): Biological evidence (blood, semen, hair, skin) is collected from the crime scene. The DNA profile from this evidence is compared to the DNA profile of a suspect. A match can place the suspect at the scene.
• Paternity Claims: A child inherits 50% of their DNA from their mother and 50% from their father. A DNA fingerprint is created for the child, the mother, and the alleged father. Every band in the child's DNA profile must be found in either the mother's or the father's profile. If the child has bands that do not match either, the alleged man is not the biological father.

Introduction to DNA Fingerprinting

DNA fingerprinting does not compare the entire 3-billion-letter genome. Instead, it focuses on specific, highly variable regions of DNA (often called "junk DNA") that are unique to each individual. Two key techniques are PCR and RFLP.

PCR (Polymerase Chain Reaction)

• Purpose: To amplify (make many copies of) a tiny sample of DNA. Crime scenes often yield only a few cells, which is not enough to test. PCR acts as a "DNA photocopier."
• Process: The DNA is mixed with primers (starting signals), nucleotides (A,T,C,G), and a heat-stable DNA polymerase (Taq polymerase). The mixture is repeatedly heated and cooled:
  1. Denaturation (95°C): Heat separates the two DNA strands.
  2. Annealing (55°C): Primers bind to the target sequences.
  3. Extension (72°C): Taq polymerase copies the DNA.
• Result: One copy of DNA becomes millions of copies in just a few hours.

RFLP (Restriction Fragment Length Polymorphism)

• Purpose: The classic method for creating a DNA "fingerprint."
• Mechanism:
  1. DNA is cut using restriction enzymes.
  2. These enzymes cut at specific sequences. Because every person's DNA is slightly different, the enzymes will cut in different places, creating fragments of different lengths (polymorphisms).
  3. These fragments are separated by size using gel electrophoresis.
  4. The resulting pattern of bands is unique to the individual.