Genetics and Biotechnology

MYP Unit Framework

Key Concept: SYSTEMS Related Concepts: Function. Models. Patterns. Global Context: Scientific and Technical Innovation (How does understanding genetic systems allow us to model, predict, and manipulate biological processes?) Statement of Inquiry: Understanding genetic systems allows us to model inheritance and manipulate biological processes through biotechnology.

Inquiry Questions

1. DNA — The Molecule of Life

The Discovery

'In 1953, James Watson and Francis Crick, using X-ray crystallography data from Rosalind Franklin, proposed the DOUBLE HELIX model of DNA. It was one of the most IMPORTANT scientific discoveries of the 20th century — comparable to Newton's laws or Einstein's relativity.'

The Structure

'DNA (deoxyribonucleic acid) is a DOUBLE-STRANDED molecule. Each strand is a polymer of NUCLEOTIDES. Each nucleotide consists of a phosphate group, a sugar (deoxyribose), and a NITROGENOUS BASE.'

The four bases:

• Adenine — pairs with Thymine (two hydrogen bonds)
• Guanine — pairs with Cytosine (three hydrogen bonds)

'The BASE-PAIRING RULES (A–T, G–C) are the KEY to DNA's function. They allow DNA to be REPLICATED ACCURATELY — and they allow the information in DNA to be TRANSCRIBED into RNA and TRANSLATED into protein.'

DNA Packaging

'In eukaryotic cells, DNA is wrapped around proteins called HISTONES and packaged into CHROMOSOMES. Humans have 23 pairs of chromosomes — 46 in total. Each chromosome contains a SINGLE, CONTINUOUS DNA molecule. If you stretched out all the DNA in a single human cell, it would be about 2 metres long. Packed inside a nucleus that is about 6 micrometres across — that is the equivalent of packing 40 KILOMETRES of thread into a TENNIS BALL.'

2. DNA Replication and Protein Synthesis

Replication — Copying the Code

'Before a cell divides, it must COPY its DNA so that EACH daughter cell receives a complete set of genetic instructions. DNA replication is SEMI-CONSERVATIVE — each new DNA molecule consists of ONE original strand and ONE newly synthesised strand.'

Key enzymes: DNA helicase (unwinds the double helix). DNA polymerase (adds complementary nucleotides). DNA ligase (seals gaps between fragments).

Protein Synthesis — From Gene to Trait

'The CENTRAL DOGMA of molecular biology: DNA → RNA → PROTEIN. Information flows from DNA to RNA (transcription) and from RNA to protein (translation).'

Transcription: 'A gene is TRANSCRIBED into messenger RNA (mRNA). RNA polymerase binds to the gene's PROMOTER region and synthesises a complementary mRNA strand. In eukaryotes, the mRNA is PROCESSED — introns are removed, exons are spliced together, and a cap and tail are added.'

Translation: 'The mRNA is TRANSLATED into a protein by RIBOSOMES. The genetic code is read in TRIPLETS (codons). Each codon codes for a specific AMINO ACID. Transfer RNA (tRNA) molecules bring the correct amino acids to the ribosome. The amino acids are linked together to form a POLYPEPTIDE chain, which folds into a FUNCTIONAL protein.'

'The genetic code is (nearly) UNIVERSAL — the same codon codes for the same amino acid in bacteria, plants, fungi, and humans. This UNIVERSALITY is powerful EVIDENCE for COMMON ANCESTRY — and is what makes GENETIC ENGINEERING possible.'

3. Mendelian Genetics — The Patterns of Inheritance

Mendel's Experiments

'Gregor Mendel (1822–1884), an Austrian monk, experimented with pea plants in his monastery garden. He tracked SEVEN traits — seed shape, seed colour, flower colour, pod shape, pod colour, flower position, and stem height. His work laid the FOUNDATION of modern genetics.'

Mendel's Laws

Punnett Squares and Probability

'Punnett squares allow us to PREDICT the probability of inheriting specific genotypes and phenotypes. A MONOHYBRID cross (tracking ONE trait) with two heterozygous parents (Aa × Aa) yields a 3:1 PHENOTYPIC ratio (dominant:recessive) and a 1:2:1 GENOTYPIC ratio (AA:Aa:aa).'

Incomplete Dominance, Codominance, and Sex-Linked Traits

'Not all traits follow SIMPLE dominant-recessive patterns. In INCOMPLETE dominance, the heterozygote has an INTERMEDIATE phenotype (red + white = pink). In CODOMINANCE, BOTH alleles are expressed (ABO blood type). SEX-LINKED traits (like colour blindness and haemophilia) are carried on the X chromosome and affect males and females DIFFERENTLY.'

4. Biotechnology — Reading and Editing Genes

Genetic Engineering

'Genetic engineering is the DIRECT manipulation of an organism's genes. The basic technique: (1) Isolate the gene of interest. (2) Insert it into a VECTOR (often a plasmid). (3) Introduce the vector into a HOST organism. (4) The host organism produces the PROTEIN encoded by the gene.'

Applications: Bacteria that produce human insulin. Genetically modified crops (Bt cotton, Golden Rice). Gene therapy for inherited diseases.

CRISPR-Cas9 — The Genome Editing Revolution

'CRISPR-Cas9 (often called "CRISPR") is a gene-editing tool ADAPTED from a natural bacterial defence system. It is CHEAPER, FASTER, and MORE PRECISE than any previous gene-editing technology. It has REVOLUTIONISED genetic research.'

How it works: 'A guide RNA leads the Cas9 enzyme to a SPECIFIC DNA sequence. Cas9 cuts the DNA at that location. The cell's natural DNA repair mechanisms then either DISRUPT the target gene (gene knockout) or INSERT a new sequence (gene editing).'

Applications: 'Correcting disease-causing mutations (sickle cell anaemia, cystic fibrosis). Creating disease-resistant crops. Engineering mosquitoes that cannot transmit malaria. Reviving extinct species (de-extinction).'

5. The Ethical Debate — Designer Babies

The Possibility

'In 2018, Chinese scientist He Jiankui announced that he had created the FIRST gene-edited babies — twin girls whose genomes he had modified using CRISPR to make them RESISTANT to HIV infection. The scientific community responded with OUTRAGE. He was condemned for UNETHICAL, UNSAFE, and UNNECESSARY experimentation on human embryos. He was sentenced to three years in prison.'

The Question

'He Jiankui's experiment was WIDELY condemned. But the technology EXISTS. It is IMPROVING. At some point, it will likely be SAFE to edit the human germline. The question then becomes: SHOULD we?'

Arguments FOR:

• 'We have a MORAL OBLIGATION to prevent suffering. If we can eliminate genetic diseases (Huntington's, cystic fibrosis, BRCA-related cancers), we SHOULD.'
• 'Germline editing is not different in PRINCIPLE from other reproductive technologies (IVF, embryo screening). It is a DIFFERENCE of DEGREE, not of KIND.'

Arguments AGAINST:

• 'It opens the door to "DESIGNER BABIES" — parents selecting for intelligence, height, eye colour, athletic ability. This is EUGENICS by another name.'
• 'It would DEEPEN inequality — only the wealthy could afford genetic enhancement, creating a GENETIC DIVIDE between the "enhanced" and the "natural."'
• 'We do not fully understand the LONG-TERM consequences. Germline edits will be passed down to FUTURE GENERATIONS — and we have not asked their CONSENT.'

Your Summative Assessment — The Ethics of Genetic Engineering Report

Task: Choose ONE biotechnology application (GMOs, gene therapy, CRISPR germline editing, genetic testing, or another approved topic) and write a 1200–1500 word scientific report. Your report must: (1) Explain the UNDERLYING SCIENCE clearly. (2) Describe the CURRENT APPLICATIONS and potential FUTURE uses. (3) Analyse the ETHICAL arguments for and against. (4) State and JUSTIFY your own position. (5) Include at least THREE scientific sources.

'This assessment integrates SCIENTIFIC understanding with ETHICAL reasoning — a key skill for IB DP Sciences and TOK.'

ATL Skills

Formative Assessments

Interdisciplinary Connections

• Chemistry: Chemical structure of DNA and proteins. Hydrogen bonding in base pairing.
• Mathematics: Probability in inheritance patterns. Punnett squares and statistics.
• TOK: What counts as 'evidence' in genetics? How do VALUES influence decisions about biotechnology?
• Language & Literature: Ethical arguments and persuasive writing about science.

Service as Action

• Genetic literacy awareness: Create materials to educate the school community about genetic testing and its implications.
• Science fair project: Design a genetics-related investigation for the school science fair.
• Bioethics debate club: Start or join a club that debates ethical issues in biotechnology.

IB Learner Profile Attributes

Self-Test Questions

1. Draw and label the structure of a DNA nucleotide. Explain the base-pairing rules.

2. Explain the CENTRAL DOGMA of molecular biology. What are the key steps and molecules involved?

3. State Mendel's TWO laws and give an example of each.

4. A heterozygous pea plant (YyRr) is crossed with itself. What is the probability of a YYRR offspring? Show your working.

5. What is CRISPR-Cas9? Describe how it works and give TWO applications.

6. List TWO arguments FOR and TWO arguments AGAINST human germline editing.

7. 'GMOs are dangerous and should be banned.' Write a response that includes BOTH the scientific evidence and the ethical considerations.