IB MYP 4-5 Biology-DNA and Genetics- Study Notes - New Syllabus
IB MYP 4-5 Biology-DNA and Genetics- Study Notes – New syllabus
IB MYP 4-5 Biology-DNA and Genetics- Study Notes – IB MYP 4-5 Biology – per latest IB MYP Biology Syllabus.
Key Concepts:
- DNA structure and replication
- Protein synthesis
- Genetic engineering applications
DNA Structure and Replication
What is DNA?
- DNA stands for Deoxyribonucleic Acid. It is the genetic material found in the nucleus of almost every cell.
- DNA carries instructions for how living things look, grow, function, and reproduce.
Structure of DNA – The Double Helix
DNA looks like a twisted ladder this shape is called a double helix.
What is DNA made of?
DNA is made up of repeating units called nucleotides. Each nucleotide contains:
- Sugar (deoxyribose)
- Phosphate group
- Nitrogen base (A, T, C, or G)
The Four Nitrogen Bases
| Base | Full Name | Pairs With |
|---|---|---|
| A | Adenine | T (Thymine) |
| T | Thymine | A (Adenine) |
| C | Cytosine | G (Guanine) |
| G | Guanine | C (Cytosine) |
These form the “rungs” of the DNA ladder.
Why is DNA Important?
- Stores genetic instructions (genes)
- Controls which proteins cells make
- Passes traits from parent to offspring
- Used in medicine, ancestry tests, and forensics
DNA Replication – Copying DNA
Before a cell divides, it makes an exact copy of its DNA. This ensures each new cell has the same instructions.
Steps in DNA Replication:
- DNA unzips: Enzyme breaks weak hydrogen bonds between base pairs
- Two strands separate
- Free nucleotides match A with T and C with G
- Two identical DNA molecules form
Summary Table
| Feature | Details |
|---|---|
| DNA stands for | Deoxyribonucleic Acid |
| Shape | Double helix |
| Made of | Nucleotides |
| Bases | A, T, C, G |
| Base pairs | A-T, C-G |
| Location in cell | Nucleus |
| Function | Stores genetic information |
| DNA replication result | Two identical DNA molecules |
DNA stores the code for life in a double-helix structure. During cell division, it is copied exactly using base pairing, so all cells carry the same genetic instructions.
Protein Synthesis
What Is Protein Synthesis?
Protein synthesis is the process by which cells build proteins using the genetic instructions stored in DNA.
- Proteins are essential for structure, enzymes, hormones, and cellular functions.
- They control chemical reactions and support almost every body function.
Two Main Stages of Protein Synthesis
- Transcription – DNA → mRNA (in the nucleus)
- Translation – mRNA → protein (in the ribosome)
Stage 1: Transcription (Making mRNA)
Location: Nucleus
A gene on the DNA is copied into a messenger RNA (mRNA) strand.
Key enzyme: RNA polymerase
Base pairing rules:
- A (DNA) → U (RNA)
- T → A, C → G, G → C
Stage 2: Translation (Building the Protein)
Location: Ribosome (cytoplasm)
The ribosome reads the mRNA. Transfer RNA (tRNA) brings amino acids to match each codon (3-letter code).
Example: Codon AUG = Methionine (start signal)
Summary Table – Protein Synthesis
| Stage | What Happens | Where? |
|---|---|---|
| Transcription | DNA → mRNA | Nucleus |
| Translation | mRNA → Protein (using tRNA) | Ribosome (cytoplasm) |
Why Is Protein Synthesis Important?
- Genes control traits by coding for proteins
- Proteins form enzymes and hormones
- Essential for growth, repair, and body functions
Genetic Engineering Applications
What is Genetic Engineering?
- Genetic engineering is the process of altering or inserting genes into an organism’s DNA to give it new traits or abilities.
- It involves cutting a gene from one organism and inserting it into another, using tools like enzymes and vectors (e.g., plasmids).
Why Do We Use Genetic Engineering?
- To improve health and medicine
- To grow better crops
- To protect the environment
- To study diseases and genes
1. In Agriculture – GM Crops
Genetically Modified (GM) crops have extra genes added to improve traits.
- Pest resistance (e.g., Bt cotton)
- Drought or flood tolerance
- Higher yields and longer shelf life
Example: Golden Rice – engineered to produce Vitamin A and reduce blindness in poor regions.
2. In Medicine
a. Medicine Production: Bacteria are modified to produce insulin, hormones, and vaccines.
Example: Human insulin gene inserted into bacteria → Insulin produced for diabetic patients.
b. Gene Therapy: Replaces faulty genes to treat genetic conditions like cystic fibrosis.
3. In Research and Science
- Study gene function and control
- Create model organisms (e.g., mice with human genes)
- Supports cloning, genome editing, and DNA fingerprinting
4. In Industry and Environment
- Bacteria used to clean oil spills (bioremediation)
- Enzymes from GM microbes used in detergents, food, and paper industries
Summary Table:
| Field | Use/Benefit | Example |
|---|---|---|
| Agriculture | Pest resistance, improved yield | Bt Cotton, Golden Rice |
| Medicine | Making drugs, treating diseases | Insulin, gene therapy |
| Research | Understand gene function, models | Mice with human genes |
| Industry | Enzymes, cleaning pollution | Oil-eating bacteria |