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Unit 3 Sustainability and interdependence

Unit 3 Sustainability and interdependence. Plant and animal breeding. KA 2a Manipulating heredity. Breeders have been manipulating heredity for thousands of years

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Unit 3 Sustainability and interdependence

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  1. Unit 3 Sustainability and interdependence

  2. Plant and animal breeding

  3. KA 2a Manipulating heredity • Breeders have been manipulating heredity for thousands of years • Selective breeding is the process by which selected individuals are bred together to produce offspring with desirable features e.g. improved cultivars of plants and or breeds of animals. • These improvements help us to ensure sustainable food production

  4. Manipulating heredity • Farmers and breeders select plants and animals with the required characteristics to be parents of the next generation. • This brings together desired alleles so that the offspring are more useful than the parents. • Many desirable characteristics have been bred into plant crops and animal breeds.

  5. How did we get from this …..

  6. ..to this?

  7. Grey wolf

  8. Ancestral cattle Selectively bred for beef Selectively bred for milk

  9. Selection in plants: cabbage family

  10. Sustainability and Interdependence KEY AREA 2a – Plant and Animal Breeding • Testing Your Knowledge 1 Page 252 Q 1-2 • What you should know page 263 Q 1(1-2 for pupils with no N5) • Problem Solving page 65 Q 1-3

  11. KA 2b Plant field trials • A plant field trial is a type of investigation, • set up to: • compare the performance of two different plant cultivars (e.g. conventional versus GM) under the same set of experimental conditions; • find out the effect of different environmental conditions on a new cultivar of crop plant.

  12. Designing a plant field trial Selection of treatments For each equal sized crop only one variable should be altered e.g. concentration of fertiliser. All other variables should remain constant to ensure that a fair comparison can be made.

  13. Designing a plant field trial • Once the factor to be investigated has been • decided, the following factors must be • considered: • selectionof treatments to be used; • numberof replicates to be included; • randomisationof treatments. • Example: • conducting a field trial to investigate the effect of the concentration of nitrogenous fertiliser on a new cultivar of cereal plant.

  14. Designing a plant field trial Number of replicates To minimise experimental error then a minimum of three replicates must be set up. The more replicates are set up the more reliable the results. This takes account of and minimizes variability within the sample. [Experimental error: differences in each plot and in how the experiment was carried out.]

  15. Designing a plant field trial Randomisation of treatments In this field 4 treatments (a, b, c and d) are being investigated, each repeated 3 times. If the plots in a field are treated in an orderly way then biasmay exist e.g. one side of the field may be wetter. Block A Designing a plant field trial B C Non-randomised field trial

  16. Designing a plant field trial Randomisation of treatments Randomisation helps eliminate bias. Block A B C Randomised field trial

  17. Metabolism and Survival Questions KEY AREA 2b – Plant Field Trials • Testing Your Knowledge 1 Page 252 Q 4 • What you should know page 263 Q 4-5 • Problem Solving page 65 Q 4

  18. Variation (Revision of National 5 slides 19-29) • The differences that occur both between different species and within the same species are called variation. • Variation can be: • continuous e.g. mass of seeds • discrete e.g. flower colour • Variation is caused by two factors: • inherited factors in genes from parents • environmental factors i.e. when features are affected by environment.

  19. Genetic terminology – N5 recap • PHENOTYPE • appearance of an organism • GENOTYPE • its genetic constitution • ALLELES • different forms of the same gene • [characteristic showing discrete variation is often controlled by the alleles of a single gene] • HOMOZYGOUS • having two identical alleles

  20. Genetic terminology – N5 recap • HETEROZYGOUS • having two different alleles of a gene • DOMINANT ALLELE • allele that is always expressed • RECESSIVE ALLELE • allele that is only expressed when homozygous • TRUE-BREEDING • organism that always produces the same phenotype when crossed with itself

  21. Genetic terminology – N5 recap • Characteristic Dominant trait Recessive trait • Short • Plant height • Tall • Inflated • Pod shape • Constricted • Seed colour • Green • Yellow • Seed shape • Round • Wrinkled • White • Purple • Flower colour

  22. White Mouse (bb) White Mouse (bb) Black Mouse (BB) Black Mouse (BB) X X White Mouse (bb) Black Mouse (BB) Black Mouse (BB) White Mouse (bb) X X Black Mouse (BB) White Mouse (bb) True breeding

  23. MONOHYBRID (SINGLE GENE) CROSS: • a cross involving only one difference in an inherited characteristic e.g. coat colour in mice:

  24. Black Mouse (BB) White Mouse (bb) Monohybrid cross X Black Mouse (Bb) Black Mouse (Bb) X Black Mouse (BB) Black Mouse (Bb) Black Mouse (Bb) White Mouse (bb) 3 Black Mice : 1 white mouse

  25. Monohybrid cross e.g. flower colour in peas: R – red; r - white Generation P (Parent) Red x White RRrr gametes all R all r F1(first Filial) all Red x F1 RrRr gametes R and rR and r F23 Red: 1White 1RR : 2Rr : 1rr

  26. Test cross What genotype could this brown mouse have? How can you tell if this brown mouse is BB or Bb? A test cross is a cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait.

  27. Brown mouse (?) White mouse (bb) Brown mouse (?) White mouse (bb) X X ½ brown mice ½ white mice All brown mice B b B b B b B B b B b B B b b b b B b b The genotype of the unknown mouse must have been BB The genotype of the unknown mouse must have been Bb

  28. Polygenic inheritance A characteristic showing continuous variation (e.g. height) is controlled by the alleles of more than one gene – it shows polygenic inheritance. The effect of the genes involved is additive. The greater the number of genes involved, the greater the number of intermediate phenotypes produced. Many traits showing polygenic inheritance are influenced by the environment.

  29. Metabolism and Survival Questions KEY AREA 2c – Inbreeding • Testing Your Knowledge 2 Page 256 Q 1, 2(b-e) • What you should know page 244 Q 6-11 • Problem Solving page 65 Q 8

  30. Outbreeding (Information only) Outbreeding involves the fusion of two gametes from unrelated members of the same species. Wild animals and cross-pollinating plants are naturally outbreeding e.g. crop plants such as tomatoes, sugar beet and maize. Outbreeding promotes heterozygosity.

  31. KA 2c Inbreeding Inbreeding • involves the fusion of two gametes from close relatives; • promotes homozygosity; • is naturally occurring in some species of self-pollinating plants e.g. peas, wheat and rice; • ensures that each generation receives the alleles for the desired characteristics. • [Recessive alleles are eliminated by natural selection.]

  32. Effects of inbreeding Desired effect Selected plants or animals are bred for several generations until the population breeds true to the desired type. Negative effects Lossof heterozygosity (not a problem for naturally inbreeding plants) 2. Inbreeding depression

  33. Loss of heterozygosity Heterozgosity Aa (selfed) 100% P aa F1 AA Aa Aa 50% F2 25% AA AA AA AA AA AaAaaa AA Aa Aa aa aa aa aa aa F3 12.5% 4AA 4AA 4AA 4AA 4AA AA 2Aa aa AA 2Aa aa 4aa 4AA AA 2Aa aa AA 2Aa aa 4aa 4aa 4aa 4aa 4aa

  34. Inbreeding depression If a natural outbreederis forcibly inbred, problems arise due to homozygous recessive alleles that may be harmful (usually masked). This is called inbreeding depression.

  35. Inbreeding depression This often leads to a decline in vigour, size and fertility e.g. in maize – the plant on the left is the original parent that was forcibly inbred. Inbreeding depression in maize Avoidance of depression Parent plants selected are homozygous for desired characteristics but heterozygous for others.

  36. Effects of inbreeding in humans The Vadoma tribe of Zimbabwe have Ectrodactyly (two toed feet). This mutation is more common due to inbreeding.

  37. KA2d Crossbreeding and F1 hybrids Inbreeding is not usually carried out indefinitely because of the problems associated with it. New alleles can be introduced into a plant or animal species by crossbreeding with a strain with a different but desired genotype. In animals, individuals from different breeds may produce a new crossbreed population with improved characteristics.

  38. F1 hybrids F1 hybrid: an individual resulting from a cross between two genetically dissimilar parents. Breeders cross members of one variety of a species having a desired characteristic with members of another variety that have another desired characteristic in an attempt to produce a hybrid that has both desirable characteristics.

  39. The two parent breeds can be maintained to produce more crossbreed animals showing the improved characteristic

  40. F1 hybrids In plants a cross between two different homozygous parents creates a uniform F1 generation. In inbreeding animals and plants, F1 hybrids are not usually bred together as the F2 produced shows too much variation. F1 hybrids have to always be produced from true-breeding parents therefore the parent breeds have to be maintained.

  41. Hybrid vigour • In plants F1 hybrids have increased: • vigour • yield and • fertility because recessive alleles are masked by superior dominant alleles. • disease resistance Parent 1 F1 hybrid Parent 2

  42. KA 1e Genetic technology • Plants and animals can also be enhanced by • use of genetic technologies such as • genome sequencing and genetic • transformation. • Genome sequencing can be used to identify organisms that possess alleles for a desired characteristic. • These organisms can then be used in • breeding programmes. • Genetic transformation. Single genes for desirable characteristics can be inserted into the genome of crop plants

  43. Genetic technology Genetic transformation can be used to enhance a crop species which can then be used in a breeding programme. Examples

  44. Metabolism and Survival Questions KEY AREA 2c – Genetic Technology • Testing Your Knowledge 3 Page 256 Q 1-3 • What you should know page 263 Q 12 • Problem Solving page 65 Q 9

  45. Removed material on next slide (in case they put it back in next year!!!!)

  46. Back crossing Back cross: crossing of an F1 hybrid with one of its parents or with a genetically identical individual. Back crossing may be used to incorporate a required gene from a parent while maintaining other desired features e.g. cultivated tomatoes are crossed with eelworm-resistant wild tomatoes; the F1 are back crossed with the cultivated parent for several generations until most wild genetic material (apart from resistance to eelworm) has been eliminated.

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