Lesson Notes By Weeks and Term v4 - SHS 3
BIOLOGY AND ENTREPRENEURSHIP
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BIOLOGY AND ENTREPRENEURSHIP
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Biology
Class: SHS 3
Term: 1st Term
Week: 4
Grade code: 3.1.2.LI.3
Strand code: 1
Sub-strand code: 2
Content standard code: 3.1.2.CS.1
Indicator code: 3.1.2.LI.3
Theme: EXPLORING BIOLOGY IN SOCIETY
Subtheme: BIOLOGY AND ENTREPRENEURSHIP
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This lesson introduces one of the most powerful and discussed tools in modern biology: Recombinant DNA technology. We will explore how scientists can act like "genetic surgeons," cutting and pasting genes from one organism to another to create Genetically Modified Organisms (GMOs). This technology has profound implications for our lives in Ghana and worldwide, affecting everything from the food we eat (improving crops like maize and cowpea to resist pests) to the medicine we use (producing insulin for diabetics).
A. Foundational Definitions Biotechnology: The use of living organisms or their products for practical purposes, such as making medicine, improving crops, or breaking down waste. It's biology put to work! Genetic Engineering: The direct manipulation of an organism's genes using biotechnology. It's a specific, modern form of biotechnology. Recombinant DNA (rDNA) Technology: This is the core technique of genetic engineering. It involves joining together DNA molecules from two different species. The resulting hybrid DNA is called recombinant DNA. Think of it as creating a "cut-and-paste" document, but with genetic code. Genetically Modified Organism (GMO): An organism (plant, animal, bacterium, etc.) whose genetic material (DNA) has been altered in a way that does not occur naturally by mating and/or natural recombination. B. The "Tools" for Genetic Engineering
To perform this genetic "cut-and-paste," scientists need a specific toolkit. The Gene of Interest: This is the specific segment of DNA that codes for a desirable trait. *Example:* A gene from the bacterium *Bacillus thuringiensis* (Bt) that produces a protein toxic to insects. The Vector: This is a "delivery vehicle" used to carry the gene of interest into a new host cell. The most common vectors are plasmids. Plasmids: Small, circular pieces of DNA found in bacteria, separate from their main chromosome. They can replicate independently. Think of a plasmid as a small, portable USB drive for genes. Restriction Enzymes: These are "molecular scissors." They are enzymes that cut DNA at a specific, recognised sequence of bases. *How they work:* Each restriction enzyme (e.g., EcoRI, HindIII) recognises a unique DNA sequence. When it finds this sequence, it cuts the DNA strand. Many restriction enzymes make a staggered cut, leaving short, single-stranded "sticky ends" that are ready to pair with complementary sticky ends. DNA Ligase: This is the "molecular glue." It's an enzyme that joins pieces of DNA together by forming phosphodiester bonds. It is used to paste the gene of interest into the vector after they have both been cut. The Host Organism: The cell or organism that receives the recombinant DNA. This could be a bacterium (like *E. coli*), a yeast cell, or a plant cell. C. The Process of Creating a GMO (using Recombinant DNA Technology)
Let's use a practical Ghanaian example: Creating insect-resistant cowpea (pod-borer resistant). The Council for Scientific and Industrial Research (CSIR) in Ghana has worked on this. The pest is the Maruca pod borer, and the gene of interest comes from the bacterium *Bacillus thuringiensis* (Bt).
Step 1: Isolation of DNA Isolate the Gene of Interest: Scientists extract DNA from the *Bacillus thuringiensis* (Bt) bacterium. They then use specific techniques to locate and separate the gene that produces the insect-killing protein (the Bt gene). Isolate the Vector: At the same time, they harvest plasmids from a suitable bacterium, like *Agrobacterium tumefaciens*, which is often used to transfer genes into plants.