Foothill High School Science Department Biotechnology - History Selective Breeding

Foothill High School Science DepartmentFoothill High School Science Department

Biotechnology - HistoryBiotechnology - HistoryBiotechnology - HistoryBiotechnology - History

Selective BreedingSelective BreedingSelective BreedingSelective Breeding


Selective BreedingSelective Breeding

The Wide Variety of Animals & The Wide Variety of Animals & Plants Used By Humans, Have Plants Used By Humans, Have Been Developed By Selective Been Developed By Selective

Breeding – Allowing Only Breeding – Allowing Only Those Animals & Plants With Those Animals & Plants With Desired Characteristics Are Desired Characteristics Are

Allowed To Reproduce.Allowed To Reproduce.



Key ConceptKey Concept:Humans Use Selective Breeding Humans Use Selective Breeding

To Pass Desired Traits On To The To Pass Desired Traits On To The Next Generation of OrganismsNext Generation of Organisms

–Apples, Corn, PotatoesApples, Corn, Potatoes

–Dogs, Cattle, Mice, YeastDogs, Cattle, Mice, Yeast


• Luther Burbank 1849-1926Luther Burbank 1849-1926–800 Varieties of Plants800 Varieties of Plants

• Disease Resistant PotatoesDisease Resistant Potatoes



Selective Breeding - HybridizationSelective Breeding - Hybridization

Crossing Dissimilar Individuals Crossing Dissimilar Individuals To Bring Together The Best Of To Bring Together The Best Of Both OrganismsBoth Organisms–Often Hardier Than ParentsOften Hardier Than Parents

–Disease Resistance + Increased Disease Resistance + Increased Food Producing CapacityFood Producing Capacity


Selective Breeding - HybridizationSelective Breeding - HybridizationSelective Breeding - HybridizationSelective Breeding - Hybridization

Postzygotic BarriersPostzygotic Barriers

–Reduced Hybrid ViabilityReduced Hybrid Viability• Embryos Don’t DevelopEmbryos Don’t Develop

–Reduced Hybrid FertilityReduced Hybrid Fertility• Offspring Vigorous but SterileOffspring Vigorous but Sterile

–Hybrid BreakdownHybrid Breakdown• 11stst Generation Viable & Fertile Generation Viable & Fertile• 22ndnd Generation Feeble & Sterile Generation Feeble & Sterile


Selective Breeding - Selective Breeding - InbreedingInbreedingSelective Breeding - Selective Breeding - InbreedingInbreeding

• Used To Maintain A Desired Used To Maintain A Desired CharacteristicCharacteristic– Dog BreedsDog Breeds– Higher Risk of Homozygous Higher Risk of Homozygous

Recessive Alleles for Genetic Defect.Recessive Alleles for Genetic Defect.• Blindness & Joint Problems In German Blindness & Joint Problems In German

Shepherds & Golden Retrievers Shepherds & Golden Retrievers


Increasing VariationIncreasing VariationIncreasing VariationIncreasing Variation

Key ConceptKey Concept:Breeders Can Increase The Breeders Can Increase The

Genetic Variation In A Population Genetic Variation In A Population By Inducing MutationsBy Inducing Mutations



• Selective Breeding Impossible Selective Breeding Impossible Without A Diverse Gene PoolWithout A Diverse Gene Pool– Importance Of Diversity In Wild Importance Of Diversity In Wild

PopulationsPopulations

• Mutations Induced ThroughMutations Induced Through– RadiationRadiation

– ChemicalsChemicals



• Most Mutations UndesirableMost Mutations Undesirable–Offspring DestroyedOffspring Destroyed

• Few Mutations DesirableFew Mutations Desirable–Breed To MaintainBreed To Maintain


Increasing VariationIncreasing VariationNew Kinds of BacteriaNew Kinds of BacteriaIncreasing VariationIncreasing Variation

New Kinds of BacteriaNew Kinds of Bacteria

• Easy To Induce Mutations In Easy To Induce Mutations In Millions At OnceMillions At Once

• Mutations Particularly Useful Mutations Particularly Useful –Produce Oil Eating BacteriaProduce Oil Eating Bacteria

–Plastic Eating BacteriaPlastic Eating Bacteria


Increasing VariationIncreasing VariationNew Kinds of PlantsNew Kinds of PlantsIncreasing VariationIncreasing VariationNew Kinds of PlantsNew Kinds of Plants

• Drugs Disrupt Chromosomal Drugs Disrupt Chromosomal Separation During MeiosisSeparation During Meiosis–PolyploidyPolyploidy

• Offspring 2X or 3X ChromosomesOffspring 2X or 3X Chromosomes• Usually Fatal For AnimalsUsually Fatal For Animals• Tolerated & Useful In PlantsTolerated & Useful In Plants


Increasing VariationIncreasing VariationNew Kinds of PlantsNew Kinds of PlantsIncreasing VariationIncreasing VariationNew Kinds of PlantsNew Kinds of Plants

PolyploidyPolyploidy–May Instantly Produce A New May Instantly Produce A New

Species Larger & Stronger Than Species Larger & Stronger Than Their Diploid RelativesTheir Diploid Relatives

–Bananas, Strawberries, Oats, Bananas, Strawberries, Oats, Cotton, Tobacco, WheatCotton, Tobacco, Wheat


Increasing Variation – New Kinds of PlantsIncreasing Variation – New Kinds of Plants

AllopolyploidAllopolyploid–Two Different Species From the Two Different Species From the

Same Genus To Form A Polyploid Same Genus To Form A Polyploid HybridHybrid

– Bread Wheat – Triticum aestivumBread Wheat – Triticum aestivum

• 8000 years ago8000 years ago

• Cultivated Wheat & Wild GrassCultivated Wheat & Wild Grass


AllopolyploidAllopolyploid

Polyploid Polyploid formed between formed between

two closely two closely related speciesrelated species

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Foothill High School Science Department Biotechnology - History Selective Breeding