How do humans deliberately change the genetics of organisms, and what are the implications?
Describe selective breeding, transgenic organisms and cloning, and evaluate their applications and implications
A focused answer to the WACE Year 12 Biology dot point on reproductive and cloning technologies. Covers selective breeding, transgenic organisms, reproductive and therapeutic cloning, and the ethical and biological implications with Australian examples.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
SCSA wants you to describe each technology, give a real application, and evaluate the benefits against the biological and ethical implications. A strong answer balances clear description with a reasoned discussion of consequences.
Selective breeding
Selective breeding (artificial selection) is the oldest form of genetic manipulation. Humans choose individuals with desirable traits and breed them together, so that over many generations those traits become more common. It has produced high-yield wheat, dairy cattle that give more milk, and merino sheep bred in Australia for fine wool.
A drawback is reduced genetic diversity: by repeatedly breeding from a narrow group, the gene pool shrinks, which can increase the frequency of harmful recessive conditions and leave a breed less able to resist new diseases.
Transgenic organisms
A transgenic (genetically modified) organism contains a gene transferred from another species, made using the gene technology techniques of restriction enzymes, ligase and vectors. Examples include bacteria engineered to produce human insulin, and crops modified for pest resistance or improved nutrition.
Benefits include cheaper medicines and higher crop yields. Concerns include the possible spread of inserted genes to wild relatives, effects on non-target organisms, and questions about long-term safety and corporate control of seed.
Cloning
Cloning produces genetically identical organisms or cells.
- Reproductive cloning creates a whole organism genetically identical to another, as with Dolly the sheep, produced by somatic cell nuclear transfer.
- Therapeutic cloning produces stem cells genetically matched to a patient for medical treatment, rather than a whole organism.
Reproductive cloning raises welfare concerns (low success rates, health problems in clones) and ethical questions, while therapeutic cloning raises debate about the use of embryos.
Evaluating applications and implications
A good evaluation considers several dimensions: the biological consequences (such as reduced genetic diversity or gene escape), the ethical issues (animal welfare, consent, fairness of access), the economic effects (cost, who benefits), and the regulation in place. In Australia, gene technology is regulated by the Office of the Gene Technology Regulator, which assesses risks before approving the release of genetically modified organisms.
Why this matters for continuity
These technologies show that humans can now direct the genetics of other species deliberately, accelerating change that natural processes would take many generations to produce, or producing combinations that could never arise naturally. Understanding the biology lets you assess the claims made for and against them, which is increasingly important as the technology reaches agriculture, medicine and conservation in Australia.
Exam-style practice questions
Practice questions written in the style of SCSA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WACE 20216 marksDescribe selective breeding and explain why continued selective breeding can reduce the genetic diversity of a population and increase the frequency of harmful recessive conditions.Show worked answer →
A 6 mark answer needs the process plus the diversity consequence.
- Selective breeding
- Humans choose individuals showing a desirable trait and breed them together, repeating over many generations so the alleles for that trait become more common. It is directed (artificial) selection, changing allele frequencies using existing variation rather than creating new genes.
- Reduced diversity
- Breeding repeatedly from a small group of favoured individuals means only a narrow set of alleles is passed on, so the gene pool shrinks and overall genetic diversity falls.
- Harmful recessives
- With a small breeding group, related individuals are more likely to be crossed (inbreeding), so two copies of a rare harmful recessive allele are more likely to come together in offspring, increasing the frequency of recessive conditions. Low diversity also leaves the population less able to resist new diseases.
Markers reward the choose-and-breed process, the shrinking gene pool and the increased chance of homozygous recessive offspring.
WACE 20236 marksDistinguish between reproductive and therapeutic cloning, and evaluate the use of reproductive cloning, considering both potential benefits and concerns.Show worked answer →
A 6 mark answer needs the distinction plus a balanced evaluation.
- Distinction
- Reproductive cloning produces a whole organism genetically identical to another (e.g. Dolly the sheep, by somatic cell nuclear transfer). Therapeutic cloning produces stem cells genetically matched to a patient for treatment, not a whole organism.
- Benefits of reproductive cloning
- It can reproduce animals with valuable traits (high-yield livestock), preserve endangered species and produce genetically uniform research animals.
- Concerns
- Low success rates and frequent health or developmental problems in clones raise animal-welfare issues; clones have reduced genetic diversity; and there are ethical objections, especially to any application to humans.
- Judgement
- A balanced response concludes reproductive cloning has specific agricultural and conservation uses but is limited by welfare, diversity and ethical concerns that justify strict regulation.
Markers reward the whole-organism versus stem-cell distinction and at least one benefit and one concern with an overall judgement.