3.2 Plant and Animal breeding Plant and animal breeding by manipulation of heredity: for improved plant crops, improved animal stock, to support sustainable food production. Give examples of desirable characteristics that could be selected for in breeding Plant Animal BREEDING PLANTS AND ANIMALS We are learning to • Identify what characteristics in plants and animals humans might be interested in selecting for breeding. • Describe how to set up a field trial • Identify the reasons for certain procedures during a field trial. I can…. • List what characteristics humans breed plants and animals for • Identify why a selection of treatments, a number of replicates and randomisation of samples is required in field trials. Why breed plants and animals? New and improved plant cultivar plant/animal breed 1. Increased plant yield 2. Increased nutritional value 3. Increased pest resistance 4. Increased disease resistance 5. Ability to thrive in cold, damp climate Field Trials Field Trials Carried out in a range of environments to compare the performance of a) Different cultivars b) Different treatments c) GM Crops Field Trials Divided into equal sized portions called plots. Designing a Field Trial 4 Key principles 1. Selection of treatments to be used. 2. Number of replicates to be included. 3. Randomisation of treatments. 4. Repeats in other environment 1. Selection of treatments • High concentration of fertilisers • Low concentration of fertilisers • No fertilisers Ensures fair comparison 2. Number of Replicates Uncontrolled variability exists due to experimental error. Having a minimum 3 replicates set up allows us to take account of natural variability Designing a Field Trial Treatment Replicate 1 Replicate 2 Replicate 3 High fertiliser 80% growth 83% growth 77% growth concentration Low fertiliser 65% growth 56% growth 58% growth concentration Control (no 23% growth 29% growth 12% growth fertiliser) 3. Randomisation of Treatments Randomise pattern of replicates to eliminate bias. Plot A Plot B Plot C Plot B Plot A Plot C Replicate 1 Replicate 2 • Plant field trials care used to compare the performance of different cultivars or GM crops. Explain how each of the following are involved in the design of the trial 1. Selection of treatments… Ensures fair comparison 2. Number of replicates…. Takes into account variability in sample 3. Randomisation of treatments… Eliminates bias Which of the following arrangements of plots has been set up to eliminate bias? Several replicates were included in the field trial in order to A. Randomise the treatments B. Minimise the experimental error C. Treat the plots in an orderly sequence D. Allow a fair comparison between two variable factors BREEDING PLANTS AND ANIMALS We are learning to • Describe what inbreeding is • Explain why breeders choose to inbreed species. • Re-cap how to carry out a monohybrid cross. I can…. • Carry out monohybrid crosses • Complete a definition of what inbreeding and outbreeding are Variation 1. What is Variation 2. How can variation be categorised? 3. Give an example of each type of variation Discrete Variation When a characteristic can be split into two or more groups. Presented as a bar chart Examples • Plant shape • Plant colour • Seed Shape Continuous Variation Varies in a smooth continuous way from 1 extreme to another Presented as a distribution curve Examples Height Seed mass Bell Shaped Curve Polygenetic Inheritance Continuous variation is controlled by more than 1 allele (polygenetic inheritance). The more genes involved, the more intermediates. Cattle Examples Birth weight Weaning Weight Single gene (Monohybrid) cross Seed colour is an example of discrete variation as it is controlled by the alleles of a single gene. This monohybrid cross is an example of cross fertilization or outbreeding. Re-Cap practice Carry out the following crosses: • A cross between a true-breeding (homozygous) plant with purple flowers and a true-breeding plant with white flowers. • A cross between two individuals of the F1 generation Inbreeding Fusion of 2 gametes from close relatives over many generations until the population breeds true to receive a desired result Loss of heterozygous Alleles. Inbreeding Depression • Accumulation of recessive, deleterious homozygous alleles. • Loss of heterozygous alleles which mask deleterious allele • These individuals will do less well at surviving to reproduce. Tasks: Questions 1. Give one example of a characteristic which breeders may attempt to improve in an animal or plant species 2. Pedigree dogs often suffer from health problems affecting their fitness. What do we call this phenomenon? BREEDING PLANTS AND ANIMALS We are learning to • Describe what cross breeding is • Explain how cross breeding leads to hybrid vigour • Explain how hybrid vigour can be maintained. I can…. • Answer Higher Biology exam questions • Cary out a true false quiz Cross Breeding • Individuals from different breeds produce F1 cross bred offspring with improved characteristics. • New alleles can be introduction by these means. • The two parent breeds can be maintained to produce more crossbred animals showing the improved characteristics. labradoodle puggle F1 Hybrids Animals . 1.Racehorse breeder 1.strong stallion 2. fast mare F1 Hybrids Plants 2 inbred P generation species produces relatively uniform F1 generation Marigolds Pansies Hybrid Vigour F1 has advantages over P generation 1. Increased yield/growth rate 2. Increased disease resistance 3. Increased strength/speed However F2 generation is genetically variable & of little use. Maintaining F1 Cross Breed As heterozygous F1 cross breed produces a wide variety of genotypes the F2 generation is genetically variable & of little use. Two parents are maintained to produce cross bred animals to produce F1 hybrid vigour. F1 Hybrid P generation AABBccdd x aabbCCDD F1 generation AaBbCcDd F2 generation wide variety of genotypes Many F2 lacking enhanced characteristic True or False True or False During inbreeding selected members of a species are bred for several generations until they breed true? True or False Continuous inbreeding results in a loss of homozygosity? True or False The accumulation of recessive deleterious alleles in a homozygous phenotype results in inbreeding depression? True or False Cross breeding is a way of introducing new alleles into a plant or animal line? True or False Monohybrid inheritance is a characteristic shown from the interaction of alleles of more than one gene ? GENETIC TECHNOLOGY We are learning to • Describe how gene technology can be used in plant and animal breeding programmes. I can…. • Produce a table to compare the characteristics that animals and plants are bred for. • Carry out monohybrid crosses • Complete a definition of what inbreeding and outbreeding are Find Someone Who… Genetic Technology – Re-cap 1. Genome Sequencing 2.Genetic Transformation What is genome sequencing What is genetic transformation? Use of Genome Sequencing Organisms with desirable alleles of genes identified. Used in breeding programmes to incorporate useful allele into new crop/animal breed. Single genes for desirable characteristics can be inserted into the genomes of crop plants, creating genetically modified plants with improved characteristics. Golden Rice • Clip 1 Bt Toxin Gene for Pest Resistance Glyphosate resistance crops.