Biology (0610) | Biotechnology and genetic modification

Hello Future Biologists! Welcome to Biotechnology!

This chapter, "Biotechnology and Genetic Modification," might sound like something out of a science fiction movie, but it is actually one of the most relevant and exciting areas of modern Biology! We look at how we use living organisms (mostly tiny ones like bacteria and yeast) to produce useful products or to modify them to improve crops and medicine.

Don't worry if some of the terms seem complex. We will break them down step-by-step. Let's explore how we harness the power of life!

Section 21.1: Why Bacteria are Biology's Best Friends

What is Biotechnology?

Biotechnology is simply the use of biological organisms, systems, or processes to create products or services useful to humans. Think of making bread (using yeast) or cheese (using bacteria) – that's ancient biotechnology!

Core Concept: Why Bacteria and Yeast are So Useful

Bacteria and yeast are the stars of biotechnology because they have two main advantages:

1. Rapid Reproduction Rate: They multiply extremely quickly. If you give them the right conditions, you can have millions of cells producing your desired product in just a few hours.
2. Ability to Make Complex Molecules: They have the necessary machinery (ribosomes, cytoplasm, enzymes) to make large, complex molecules, such as proteins (like hormones or enzymes) and antibiotics.

Supplement: Deeper Dive into Bacterial Advantages

For Extended students, you need to know two further reasons why bacteria are perfect hosts for genetic modification:

1. Few Ethical Concerns: Since bacteria are simple organisms (prokaryotes) and we don't consider them sentient, there are generally few ethical concerns about manipulating them or growing them in labs, unlike working with animals.
2. The Presence of Plasmids: Bacteria contain small, circular loops of DNA called plasmids, in addition to their main circular chromosome. Plasmids are easily removed, modified, and reinserted, making them the perfect "vehicles" for carrying new genes.

Section 21.2: Biotechnology in Action (Industrial Processes)

Core Applications: Everyday Biotechnology

1. Yeast and Anaerobic Respiration (Fermentation)

Yeast is a fungus used extensively in the food and fuel industries, relying on the process of anaerobic respiration (fermentation).

• Ethanol for Biofuels: Yeast breaks down sugar (glucose) without oxygen to produce ethanol (alcohol) and carbon dioxide.
  

  Glucose \(\to\) Alcohol + Carbon Dioxide (+ less energy)

  The ethanol produced is collected and used as a renewable fuel source (biofuel).

• Bread-making: The yeast in dough respires anaerobically, producing carbon dioxide gas. This gas is trapped in the dough, making it rise and giving the bread its light texture. (The ethanol evaporates during baking).

2. Enzymes in Industry

• Pectinase in Fruit Juice: Pectinase is an enzyme that breaks down pectin, a substance found in plant cell walls. When pectinase is added to crushed fruit, it breaks down the cell walls, releasing more juice and making the final product clear, not cloudy.
• Enzymes in Washing Powders: Biological washing powders contain enzymes (usually proteases, lipases, and amylases) extracted from microorganisms. These enzymes break down common stains (proteins like blood, fats like grease, and starch) even at low temperatures, making washing more efficient.

Supplement: Large-Scale and Advanced Uses

3. Lactase for Lactose-Free Milk (Enzyme Use)

Many people are lactose intolerant (they cannot digest the sugar lactose found in milk). We use the enzyme lactase (often sourced from yeast or fungi) to solve this problem.

• Lactase breaks down lactose into the smaller, more digestible sugars: glucose and galactose.
• The resulting milk is lactose-free and sweeter (because glucose and galactose taste sweeter than lactose).

4. Large-Scale Production: The Fermenter

When we need large amounts of a useful product (like insulin for diabetes, penicillin as an antibiotic, or mycoprotein for food), we grow microorganisms in huge containers called fermenters (or bioreactors).

Examples of large-scale products:

• Insulin: Human insulin gene is placed in bacteria.
• Penicillin: Produced by the fungus Penicillium.
• Mycoprotein: A high-protein meat substitute made from fungal biomass.

To keep the microorganisms happy and productive, the conditions inside the fermenter must be carefully controlled:

Controlled Conditions in a Fermenter (The "5 P's"):

1. Temperature: Needs to be optimal for the enzymes of the microorganism. Too low = slow growth. Too high = denaturation.
2. pH: Needs to be optimal for enzyme activity. Acids or alkalis are added to maintain the desired pH.
3. Oxygen Concentration: Needs constant supply (aerobic respiration) or strict absence (anaerobic respiration), depending on the product (e.g., penicillin production needs high oxygen).
4. Nutrient Supply: A continuous supply of food (e.g., glucose, minerals, amino acids) is pumped in to support rapid growth and production.
5. Waste Products Removal: Metabolic waste (like CO2, heat, or harmful toxins) must be removed to prevent them from poisoning the culture or reducing yield.

Did you know? Fermenters are continuously stirred to ensure the microbes, nutrients, and oxygen are evenly distributed throughout the huge tank!

Section 21.3: Genetic Modification (Genetic Engineering)

Core Concept: Changing the Code

Genetic modification (GM) (or genetic engineering) is the process of changing the genetic material of an organism by removing, changing, or inserting individual genes from another species. This creates a transgenic organism.

The gene inserted contains the blueprint (DNA base sequence) for a specific trait or protein, which the receiving organism will then produce.

Core Examples of Genetic Modification

1. Human Genes into Bacteria to Produce Human Proteins: The classic example is the production of human insulin. The gene coding for insulin is inserted into bacteria, which then multiply rapidly and produce massive quantities of human insulin protein for use by diabetics.
2. Genes into Crop Plants for Herbicide Resistance: Crops are modified to be resistant to specific herbicides (weed killers). Farmers can then spray fields with the herbicide, killing the weeds but leaving the genetically modified crop unharmed.
3. Genes into Crop Plants for Insect Pest Resistance: Crops are modified to produce a natural toxin (poison) that kills specific insect pests when they try to eat the plant. This reduces the need for external chemical insecticides.
4. Genes into Crop Plants to Improve Nutritional Qualities: For example, inserting genes into rice to make it produce Vitamin A (Golden Rice), helping prevent vitamin deficiencies in developing countries.

Supplement: The Step-by-Step Process of Genetic Modification

We will use the example of producing human insulin in bacteria to understand the process. This is often called recombinant DNA technology.

Imagine you want to copy a page from a book (the human gene) and insert it into a magazine that can be photocopied millions of times (the bacterial plasmid).

Step 1: Isolation of the Human Gene

• The desired human gene (e.g., for insulin) is cut out from the human DNA using special enzymes called restriction enzymes.
• These enzymes cut the DNA strands at specific recognition sequences, leaving short, single-stranded overhangs called sticky ends.

Step 2: Cutting the Bacterial Plasmid

• The bacterial plasmid (the "vehicle") is cut open using the same restriction enzyme.
• Using the same enzyme ensures the plasmid has complementary sticky ends that match the sticky ends of the human gene.

Step 3: Creating the Recombinant Plasmid

• The human gene fragments are mixed with the open plasmids.
• The sticky ends pair up.
• A second enzyme, called DNA ligase, acts like "biological glue" to join the human DNA sequence into the plasmid DNA, forming a circular recombinant plasmid.

Step 4: Insertion and Multiplication

• The recombinant plasmids are inserted back into the host bacteria (this process is called transformation).
• The bacteria are grown in a fermenter (multiplication of bacteria). Because the plasmid is part of the bacterial cell, it is copied every time the bacteria divide.

Step 5: Expression

• The bacteria now contain the instructions (the human gene) to produce the desired protein (e.g., human insulin).
• The bacteria express the human gene and the desired human protein is made. This protein is then purified and used commercially.

Supplement: Advantages and Disadvantages of Genetically Modified (GM) Crops

GM crops, such as soya, maize, and rice, offer significant benefits but also raise important concerns.

Advantages of GM Crops

• Increased Yield: Resistance to pests (less crop damage) or resistance to herbicides (less competition from weeds) leads to higher overall crop harvests.
• Improved Quality: Crops can be modified to have better nutritional value (e.g., Vitamin A in rice) or improved flavour and texture.
• Reduced Pesticide Use: Pest-resistant crops require less external spraying, which can be better for the environment and for human health.
• Adaptability: Crops can be modified to tolerate harsh conditions like drought or high salinity, making farming possible in challenging environments.

Disadvantages of GM Crops

• Concerns about Safety: Some people worry about the long-term effects of consuming GM foods on human health (though extensive studies usually suggest they are safe).
• Impact on Biodiversity: If herbicide-resistant genes spread to wild plants via pollen (gene transfer), it could create "super-weeds" that are difficult to control, potentially lowering biodiversity.
• Ethical and Social Issues: Many seed producers patent their GM seeds, meaning farmers must buy new seeds every year, which raises costs and dependence on large corporations.
• Effects on Non-Target Species: Pest-resistant crops might accidentally harm beneficial insects (like bees or butterflies) if the toxin is widespread in the plant.