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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
The key difference
Selective breeding crosses organisms with desired traits over many generations to enhance those traits. Genetic engineering directly transfers specific genes from one organism to another, even between different species, in a single step.
Both selective breeding and genetic engineering aim to produce organisms with desirable characteristics, but they use fundamentally different methods. Genetic engineering is faster and can cross species barriers, but raises additional ethical concerns. This comparison is important for Topic 21 (Biotechnology).
Feature
Selective Breeding
Genetic Engineering
Method
Choose parents with desired traits → cross them → select best offspring → repeat over generations
Identify desired gene → cut it out with restriction enzymes → insert into host organism using a vector (e.g. Plasmid)
Speed
Slow: takes many generations
Fast: one generation to introduce the gene
Species barrier
Cannot cross species barriers: can only breed closely related organisms
Can transfer genes between completely different species (e.g. Human insulin gene into bacteria)
Precision
Low: transfers many genes at once, not just the desired one
High: transfers a specific single gene
Genetic diversity
Reduces diversity through inbreeding
Does not necessarily reduce diversity (gene added to existing genome)
History
Used for thousands of years (since the start of agriculture)
Relatively new technology (since the 1970s)
Example
High-yield wheat varieties bred for larger grain heads
Bacterial production of human insulin using the inserted human insulin gene
Public acceptance
Generally well accepted: seen as "natural"
More controversial: concerns about GM foods, "playing God", ecological impacts
The Steps of Genetic Engineering
At IGCSE level, you need to know the basic steps:
Identify the gene for the desired characteristic in the donor organism
Cut the gene from the donor DNA using restriction enzymes (biological scissors)
Insert the gene into a vector (usually a bacterial plasmid) using ligase enzyme
Transfer the vector into the host organism (e.g. A bacterium)
The host organism now produces the desired protein coded by the inserted gene
The most important example is the production of human insulin by bacteria. The human insulin gene is inserted into E. Coli bacteria, which then produce human insulin in large quantities through fermentation.
Advantages and Concerns
Advantages of genetic engineering over selective breeding:
Much faster: no need to wait for many generations
More precise: only the desired gene is transferred
Can cross species barriers: genes from any organism can be used
Can produce substances that selective breeding cannot (e.g. Human proteins in bacteria)
Concerns about genetic engineering:
GM organisms could escape and affect wild populations
Inserted genes could have unexpected effects
Ethical concerns about modifying living organisms
Long-term health effects of GM foods are debated
Could be used irresponsibly (e.g. Biological weapons, designer babies)
Try a comparison question (4 marks)
Explain two advantages of using genetic engineering rather than selective breeding to produce organisms with desired characteristics. [4]
Show the answer and marking guidance
Genetic engineering is faster: the desired gene can be introduced in one generation rather than requiring many generations of selective breeding
This saves time and resources compared to the repeated crossing and selection needed in selective breeding
Genetic engineering can transfer genes between different species (cross species barriers): selective breeding can only work within closely related organisms
This allows the production of proteins that could not be made through selective breeding (e.g. Human insulin produced by bacteria)
Original Cambridge-style practice written for this site.
Common comparison mistakes
When answering a compare question, write matched pairs rather than two separate descriptions.
Saying selective breeding "modifies DNA directly": it uses traditional crossing, not DNA manipulation
Confusing vectors (plasmids) with viruses: plasmids are the most common vectors in genetic engineering
Claiming GM organisms are always dangerous: the safety depends on the specific modification and its regulation
Forgetting restriction enzymes and ligase when describing the genetic engineering process