21.1 Biotechnology and Genetic Modification Revision Notes

1. Overview

Biotechnology involves using living organisms, such as bacteria and fungi, to perform practical tasks or create useful products like food, drugs, and enzymes. Genetic modification is a specific branch of biotechnology where scientists change the DNA of an organism to give it new, desirable characteristics, such as the ability to produce human insulin.

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Key Definitions

• Biotechnology: The application of biological organisms, systems, or processes to manufacturing and service industries.
• Genetic Modification: Changing the genetic material of an organism by removing, changing, or inserting individual genes.
• Plasmid: A small, circular loop of DNA found in bacteria that is separate from the main bacterial chromosome.
• Vector: A vehicle (like a plasmid or virus) used to transfer genetic material into a cell.

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Core Content

Why Bacteria are Useful in Biotechnology

Bacteria are the primary organisms used in biotechnology for several key biological reasons:

1. Rapid Reproduction Rate

• Bacteria reproduce asexually through a process called binary fission.
• Under ideal conditions (correct temperature, moisture, and nutrient availability), some bacteria can double their population every 20 minutes.
• Link to Function: This allows for the massive, industrial-scale production of a desired product (like enzymes or hormones) in a very short amount of time.

2. Ability to Make Complex Molecules

• Bacteria have the cellular machinery (ribosomes and enzymes) required to synthesize complex organic molecules.
• By inserting specific instructions into their DNA, we can "program" them to build human proteins, such as insulin or clotting factors, which are chemically identical to those produced in the human body.

3. Simple Growth Requirements

• Bacteria do not require complex food sources; they can be grown in large vats called fermenters using basic nutrients like glucose and nitrogen sources.

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Extended Content (Extended Only)

In addition to the core reasons, there are two specific biological and social advantages to using bacteria in genetic engineering:

A. Lack of Ethical Concerns

• When using animals for research or production, there are significant ethical debates regarding animal welfare, suffering, and "playing God" with higher life forms.
• Bacteria are single-celled organisms without a nervous system. There are few ethical concerns regarding their manipulation, growth, and eventual destruction in industrial processes.

B. The Presence of Plasmids

• Structure to Function: Plasmids are small, circular loops of DNA that are separate from the main bacterial chromosome.
• Ease of Manipulation: Because they are small and distinct, plasmids are easy to extract from a bacterial cell, "cut" open using enzymes, and "paste" new genes into.
• Once the new gene is in the plasmid, it can be easily inserted back into a bacterium. The bacterium will then follow the instructions in the plasmid to produce the new protein.

C. Universal Genetic Code

• The DNA code is the same for all living things (it is "universal"). This means a bacterium can read a human gene and assemble the exact same sequence of amino acids to make a human protein.

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Key Equations

While there are few specific formulas for this sub-topic, you may be asked to calculate bacterial population growth.

• Bacterial Population Calculation: $N = N_0 \times 2^n$
  • $N$: Final number of bacteria
  • $N_0$: Initial number of bacteria
  • $n$: Number of generations (calculated by: $\text{Total time} \div \text{Doubling time}$)
• Units: Bacteria are measured in whole numbers; time is usually in minutes or hours.

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Common Mistakes to Avoid

• ❌ Wrong: Saying bacteria are used because they are "cheap."
• ✅ Right: Saying they are used because they have simple nutrient requirements and rapid reproduction rates.
• ❌ Wrong: Thinking the plasmid is the same thing as the main bacterial DNA.
• ✅ Right: Identifying the plasmid as a small, extra-chromosomal piece of DNA used as a vector.
• ❌ Wrong: Suggesting that genetic modification changes the "species" of the bacteria.
• ✅ Right: Explaining that it allows the bacteria to produce specific human proteins while remaining bacteria.

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Exam Tips

• Command Words:
  • "State": If asked to "State why bacteria are used," keep it simple: "Rapid reproduction" or "Presence of plasmids."
  • "Suggest": If asked to "Suggest why people prefer using bacteria over sheep for insulin," mention the ethical concerns or cost-effectiveness.
• Typical Questions: You are likely to see questions asking you to identify parts of a bacterial cell (specifically the plasmid) or to explain the benefits of using bacteria in a fermenter.
• Real-World Context: Human Insulin is the most common example used in exams. Be prepared to explain how bacteria are the "factory" that produces it.
• Numerical Values: Be comfortable with large numbers. In 24 hours, a single bacterium can theoretically produce millions of offspring; ensure you can work with values like $2 \times 10^6$ or large growth constants (e.g., 2000.0 units of product).