Genetics & Breeding
Population Size, Selection Intensity & Genetic Drift
Small breeding populations can lose alleles by chance, while strong selection can intentionally narrow diversity. Population size and selection intensity therefore shape what variation remains available in later generations.
Key concepts
- Genetic drift is stronger in small populations
- Selecting very few parents creates a bottleneck
- Rare alleles can disappear even without negative selection
- Maintaining multiple families can preserve options for later comparison
What to measure or observe
- Record total population and selected parent counts
- Track family representation
- Document why each selected parent was retained
- Preserve seed from alternate lines when diversity matters
Common mistakes
- Treating ten plants as representative of a highly variable population
- Selecting one standout without considering family structure
- Confusing random loss with intentional selection
- Discarding all unselected lineages before evaluation is complete
Visuals this lesson still needs
- Population bottleneck diagram
- Selection-intensity funnel
- Genetic drift simulation graphic
- Family representation chart