Biology (0610) | Biotechnology

🧬 Chapter 21: Biotechnology and Genetic Modification Study Notes 🔬

Hello Biologists! This chapter is one of the most exciting areas of science because it looks at how we can use living organisms—especially tiny ones like bacteria and yeast—to solve big human problems, from making medicine to improving our food supply. Don't worry if the words sound complicated; we'll break down the processes step-by-step!

Biotechnology is simply the use of biological processes, organisms, or systems to manufacture products or provide services.

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21.1 The Power of Microbes: Why Bacteria are Biology's Best Friends

Why are Bacteria Useful in Biotechnology? (Core & Supplement)

Bacteria and fungi (like yeast) are the workhorses of biotechnology due to several key features:

• Rapid Reproduction Rate: Bacteria reproduce extremely quickly (sometimes doubling every 20 minutes) via asexual reproduction.
  Why this matters: If you insert a useful gene into one bacterium, you can have millions of identical 'factories' producing your product within hours!
• Ability to Make Complex Molecules: They possess the necessary machinery (ribosomes, enzymes) to read genetic codes and build complicated substances like human proteins.
• Few Ethical Concerns (Supplement): Since bacteria are simple, single-celled organisms, using and manipulating them usually raises fewer ethical issues compared to modifying animals or humans.
• Presence of Plasmids (Supplement): This is perhaps their most important feature for genetic modification.
  A plasmid is a small, circular ring of DNA found naturally in the cytoplasm of bacteria (separate from the main circular chromosome). Plasmids are easily isolated, cut, and inserted back into the bacteria, making them perfect vectors (carriers) for new genes.

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21.2 Biotechnology in Action

Biotechnology isn't just about high-tech genetic engineering; it also includes traditional methods like using yeast for centuries!

Yeast and Anaerobic Respiration (Core)

Yeast is a type of fungus used widely in industrial processes because it can perform anaerobic respiration (respiration without oxygen).

The word equation for anaerobic respiration in yeast is:

glucose → alcohol (ethanol) + carbon dioxide

1. Ethanol for Biofuels

The ethanol produced by yeast fermentation is collected and used as a cleaner-burning fuel source (biofuel).

2. Bread-Making

Yeast is mixed with flour and water. The yeast respires anaerobically, producing carbon dioxide gas. It is this gas that forms bubbles, causing the dough to rise and giving bread its light, airy texture.

Using Enzymes in Food Production and Industry (Core & Supplement)

1. Pectinase in Fruit Juice Production (Core)

When you crush fruit, the juice is cloudy because of substances called pectins, which are found in the plant cell walls.

We add the enzyme pectinase to the crushed fruit pulp. Pectinase breaks down the pectin, helping to release more juice and making the juice much clearer (clarification).

2. Biological Washing Powders (Core)

These powders contain enzymes that help remove specific types of stains, even at low temperatures:

• Proteases break down protein stains (like blood or grass).
• Lipases break down fat/oil stains (like grease).

3. Lactase for Lactose-Free Milk (Supplement)

Some people are lactose intolerant (they cannot digest the milk sugar, lactose).

The enzyme lactase is added to milk. It breaks down the disaccharide lactose into the smaller, easily digestible monosaccharides: glucose and galactose. The resulting milk is safe for lactose intolerant people to consume.

Large-Scale Production using Fermenters (Supplement)

To produce large quantities of valuable substances (like insulin or antibiotics) safely and efficiently, we use giant containers called fermenters (or bioreactors).

Key Products Made in Fermenters:

• Insulin: A human protein hormone used to treat Type 1 diabetes. Produced by genetically modified bacteria.
• Penicillin: An antibiotic produced by the fungus Penicillium.
• Mycoprotein: A protein-rich food source (e.g., Quorn) made from the fungus Fusarium.

Control Conditions in a Fermenter: (Essential for Extended Students)

For the microbes to grow quickly and produce the maximum amount of product, several conditions must be tightly controlled:

1. Temperature: Maintained at the optimum temperature for the specific enzymes in the microorganism to function best. Too high, and the enzymes denature.
2. pH: Monitored and kept at the optimum pH using acids and alkalis, again to prevent enzyme denaturation.
3. Oxygen Supply: Air (oxygen) is usually pumped in for aerobic respiration (needed for many processes, like penicillin production). If the product requires anaerobic respiration (like ethanol), oxygen is excluded.
4. Nutrient Supply: A sterile nutrient broth (containing glucose, ions, etc.) is constantly added. This provides raw materials for growth and metabolism.
5. Waste Products: Metabolic waste (like CO₂ or heat) must be removed. If waste builds up, it can poison or slow down the microbial growth.

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21.3 Genetic Modification (Genetic Engineering)

Genetic modification (GM) is the process of changing the genetic material of an organism by removing, changing, or inserting individual genes. The resulting organism is called a genetically modified organism (GMO).

Examples of Genetic Modification (Core)

1. Human Proteins in Bacteria: Inserting the human gene for insulin into bacteria so that the bacteria mass-produce this vital hormone.
2. Herbicide Resistance in Crops: Inserting genes into crop plants (e.g., soya) so they are resistant to specific chemical weed killers (herbicides). This means the farmer can spray the fields, killing the weeds but not the crop.
3. Pest Resistance in Crops: Inserting genes (like the Bt toxin gene) into crop plants (e.g., maize) so the plant produces a toxin that kills insects that feed on it. This reduces the need for chemical insecticides.
4. Improved Nutritional Qualities: Inserting genes into crops to boost their vitamin content, such as Golden Rice, which produces beta-carotene (used to make Vitamin A).

The Process of Genetic Modification (Supplement)

Let's outline the steps using the example of producing human insulin in bacteria. This process requires three crucial biological "tools": Restriction Enzymes, Plasmids, and DNA Ligase.

1. Isolation of the Human Gene (The Cut):
   The specific human gene (e.g., for insulin) is identified. Restriction enzymes are used to cut the DNA segment making up the gene. These enzymes cut the DNA strands unevenly, leaving short, single-stranded overhangs called sticky ends.
   Analogy: Restriction enzymes are like microscopic scissors that cut DNA at precise points.
2. Cutting the Bacterial Plasmid (The Matching Cut):
   A bacterial plasmid is removed. The *same* type of restriction enzyme used in Step 1 is used to cut the plasmid DNA. This ensures the plasmid also has complementary sticky ends—they fit perfectly with the human gene.
3. Insertion and Joining (The Paste):
   The isolated human gene fragment is mixed with the cut plasmid. Because the sticky ends are complementary, they match up. The enzyme DNA ligase is then used to form chemical bonds, permanently joining the human DNA and the plasmid DNA. The new structure is called a recombinant plasmid.
   Analogy: DNA Ligase is the microscopic superglue.
4. Insertion into Bacteria:
   The recombinant plasmids are mixed with bacteria. The bacteria take up the plasmids (this process is sometimes called transformation). (Specific details of this insertion step are not required.)
5. Multiplication and Expression:
   The bacteria containing the recombinant plasmids multiply rapidly in a fermenter. Every time the bacteria divide, they copy the plasmid (and the inserted human gene). The bacteria then read the human gene's instructions and produce the human protein (e.g., insulin).

Did you know? Before genetic modification, insulin for diabetics had to be extracted from the pancreases of pigs and cows, which sometimes caused allergic reactions in humans. GM human insulin is much purer and safer!

Advantages and Disadvantages of Genetically Modifying Crops (Supplement)

Genetically modified crops (like soya, maize, and rice) offer huge benefits, but also carry risks:

Advantages of GM Crops:

• Increased Yield: By resisting pests and diseases, or tolerating specific herbicides, a greater quantity of crop can be harvested, addressing global food shortages.
• Reduced Pesticide Use: Pest-resistant crops require less chemical spraying, which is better for the environment and human health.
• Improved Quality: Genes can be added to improve nutritional content (e.g., Golden Rice providing Vitamin A).
• Wider Growing Range: Crops can be modified to tolerate harsh conditions like drought or high salinity.

Disadvantages of GM Crops:

• Ecological Risk: There is a fear that the new gene (e.g., herbicide resistance) could spread via pollen to wild relatives, creating "superweeds."
• Pest Resistance Development: If all crops contain the pest-resistance gene, the pests may quickly evolve resistance, making the technology useless over time.
• Ethical Concerns: Concerns about the long-term safety of consuming GM foods (though scientific evidence generally supports safety).
• Biodiversity Concerns: Relying heavily on a few GM varieties could reduce the overall genetic diversity of crop species, making them vulnerable to new diseases.