Plant Breeding, Genetics and Biotechnology
Genetics and plant breeding tests inheritance, selection, heterosis, mutation, biotechnology and seed production. Expect ratio problems and concept matching.
Core concepts
- Mendelian ratios: monohybrid F₂ 3:1; dihybrid 9:3:3:1; test cross 1:1.
- Self-pollinated crops use pureline selection; cross-pollinated crops use mass selection and recurrent selection; hybrid breeding uses heterosis.
- Backcross transfers a trait; pedigree maintains records; mutation creates variability; polyploidy changes fertility.
- Biotechnology includes tissue culture, micropropagation, somaclonal variation, molecular markers, transgenics and CRISPR.
- DUS testing and seed certification are distinct processes: DUS supports variety protection; certification verifies seed quality.
Worked example
Cross Aa × Aa. Probability of aa = 1/4. In 400 seedlings, expected aa = 100. Probability of A_ = 3/4 = 300. Reason: alleles segregate independently; do not double-count genotypes.
Traps
- Confusing genotype and phenotype.
- Assuming linkage still gives 9:3:3:1.
- Treating somaclonal variation as transgenic.
- Mixing seed certification with variety release.
- Forgetting cytoplasmic inheritance.