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VCE Biology Unit 3 AOS 1
Molecules of Life: DNA vs RNA
At the heart of cellular function are nucleic acids, the molecules that store and transmit genetic information. This section provides an interactive comparison of the two primary types: DNA, the master blueprint, and RNA, the versatile messenger. Click on the features below to highlight the key differences.
DNA (Deoxyribonucleic Acid)
The permanent, stable archive of genetic instructions.
- Strands: Typically two (double helix).
- Sugar: Deoxyribose.
- Bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T).
RNA (Ribonucleic Acid)
The transient, versatile copy used for protein synthesis.
- Strands: Typically one (single-stranded).
- Sugar: Ribose.
- Bases: Adenine (A), Guanine (G), Cytosine (C), Uracil (U).
From Gene to Protein: The Central Dogma
Gene expression is the fundamental process by which the information in DNA is converted into a functional protein. This interactive diagram breaks the process into three key stages. Click through the steps to see how a gene is transcribed, processed, and finally translated.
NUCLEUS
5′-…G-C-A-T-T-G-C-A…-3′
RNA Pol
CYTOPLASM
Ribosome
🔵-🔶-🟢
Gene Regulation: The *trp* Operon
Cells must control which genes are expressed to conserve energy. The *trp* operon in *E. coli* is a classic example of a repressible system that produces tryptophan. Toggle the switch below to see how the presence or absence of tryptophan controls the entire pathway.
Tryptophan Absent
Tryptophan Present
Promoter
Operator
trpE
trpD
…
RNA Pol
Active Repressor
Operon is ON
With no tryptophan present, the repressor protein is inactive. RNA Polymerase is free to bind to the promoter and transcribe the genes needed to synthesize tryptophan.
The Architecture of Function: Protein Structure
A protein’s function is dictated by its specific 3D shape. This shape is built in a hierarchy of four levels, starting from a simple chain of amino acids. Click the cards to explore each level of protein structure.
1° Primary
The linear sequence of amino acids in a polypeptide chain.
2° Secondary
Local folding into α-helices and β-pleated sheets via hydrogen bonds.
3° Tertiary
The overall 3D shape from R-group interactions.
4° Quaternary
The arrangement of multiple polypeptide subunits.
Select a level to learn more.
The Scientist’s Molecular Tools
Modern genetic engineering is possible thanks to a toolkit of specialized enzymes, mostly borrowed from bacteria. These molecular machines allow scientists to cut, paste, and copy DNA with precision. Click on each tool to reveal its function.
✂️
Restriction Enzymes
The Molecular Scissors
💧
DNA Ligase
The Molecular Glue
📠
Taq Polymerase
The Molecular Photocopier
Core Techniques: PCR & Gel Electrophoresis
Two complementary techniques form the bedrock of DNA analysis. PCR amplifies tiny amounts of DNA into usable quantities, while Gel Electrophoresis separates the resulting fragments by size, allowing for visualization and comparison.
Polymerase Chain Reaction (PCR)
Exponentially amplifies a target DNA sequence.
Gel Electrophoresis
Separates DNA fragments by size using an electric current.
Wells
+
–
A Revolution in Editing: CRISPR-Cas9
CRISPR-Cas9 is a powerful and precise genome editing tool, adapted from a natural bacterial immune system. It uses a guide RNA to direct the Cas9 enzyme to a specific DNA sequence, where it makes a precise cut. This interactive model shows the key steps of this revolutionary technology.
…GATTACA…
Cas9
guide RNA
💥
Click the button to begin the gene editing process.
Biotech in Action: Case Studies
The principles of genetic engineering have led to groundbreaking applications in medicine and agriculture. Explore these case studies to understand how recombinant DNA technology is used to produce human insulin and create genetically modified organisms (GMOs).
