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Chapter 3

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  1. Chapter 3 Heredity and Reproduction Original Power Point Created by Chris Clemons Modified by Georgia Agricultural Education Curriculum Office June 2002

  2. Heredity and Reproduction Read pages 43-45 • A plant or animal is only as developed as its genetic components. • An animal or plant receives its characteristics from its parents. • Scientists are continuously searching for improved crop and animal varieties through Selective Breeding.

  3. Heredity and Reproductionpage 43 • The first major breakthrough in plant breeding occurred in the 1930’s with the development of hybrid seed. • Hybrid seed produce 25% to 50% greater yields than traditional corn varities. • Why would hybrids produce more seed? • What is drawback to hybrids and how do researchers control this?

  4. Heredity and Reproductionpage 43 • Plant breeders use knowledge of genetics and heredity to design plant breeding programs. • A combination of traditional and molecular techniques are used. • Scientists believe that there are about 50 controllable traits in plants that can be produced through plant breeding.

  5. Heredity and Reproductionpage 45 • Controllable traits include: Palatability Heat and drought tolerance Shape and color Oil Starch, sugar, protein Fiber content, height, salt tolerance, flavor Texture, and time to maturity

  6. Chapter 3 Objectivespage 45 1. How is inheritance of traits in plants regulated? 2. How do dominant and recessive genes affect plant characteristics? 3. How does pollination in plants occur? 4. Why are some plants unable to self pollinate? 5. How do scientists use principles of plant genetics to guide their plant breeding programs? 6. How is biotechnolgy being used to supplement traditional plant breeding programs?

  7. Answer these questions 1. What is selective breeding? 2. Identify five controllable traits that scientists can control. 3. Which types of combinations are used in plant breeding. 4. What percent does hybridization increase yield by. 5. When and what was the first major breakthrough in plant breeding?

  8. Flowering and Pollination • Two major plant classifications are the Gymnosperms and the Angiosperms. • These include flowering plants, grasses, and cereals.

  9. Flowering and Pollination • All angiosperms develop flowers which contain one or more ovules that are enclosed in an ovary or carpel. • The flower is the reproductive structure for the angiosperms.

  10. Flowering and Pollination • A flower is complete if it has all four of the the following structures: Sepals, Petals, Stamens, and a Carpel (pistil)

  11. Flowering and Pollination • An incomplete flower lacks one or more of the before mentioned structures.

  12. Flowering and Pollination • A flower that has both stamens (male reproductive tissues) and a carpel (female reproductive tissues) is a perfect flower. • Imperfect flowers have either stamens or a carpel, but not both.

  13. Answer These Questions • 1. Identify the two major classifications of plants. • 2. The flower is the ____________ of the angiosperms. • 3. A complete flower has four structures, identify them. • 4. A flower which has both male and female is tissues is which type of flower? • 5. If a flower has either stamen or a carpel, which type of flower is this?

  14. Flowering and Pollination • The sepals and petals help to attract insects to the plant by producing a sugary solution called nectar.

  15. Flowering and Pollination • An incomplete flower is one which has no sepals or petals. • Most cereal and grass plants have incomplete flowers, which makes the flowers less visible.

  16. Flowering and Pollination • Flowering is initiated by: • Length of uninterrupted darkness (photoperiodism) • Exposure to low temperatures (vernalization) • Morphological maturity (able to produce seed)

  17. Flowering and Pollination • The majority of food-producing plants induce flowering without external stimulation. • As long as they are actively growing, they initiate flowers at almost any temperature or day length.

  18. Flowering and Pollination • The Stamen, consists of the Anthersand their supporting their supporting filament. • The development of pollen grains (microspores) occurs in the Anthers.

  19. Flowering and Pollination • As the Anther matures, they break open and pollen grains are spread by the wind and insects.

  20. Flowering and Pollination • The Carpel, includes the Stigma, Style, and Ovary. • The Stigma is the swollen end of the Style, is colorful and allows for the pollen to stick. • Pollen grain must land on the Stigma in order for pollination to occur.

  21. Answer these questions • 1. What does the Carpel include? • 2. Where does the development of the pollen grain occur. • 3. What is the photoperiodism? • 4. What is meant by morphological maturity? • 5. A flower which has no sepals or petals is which type of flower.

  22. Flowering and Pollination • Self-pollination occurs when the anther and the stigma are from the same flower. • From different flowers on the same plant. • From different plants of the same cultivar or variety. • Cross-pollination involves different flowers on plants or different cultivars.

  23. Flowering and Pollination • Some plants are self-fertile and produce fruit and seed without the transfer of pollen form another cultivar. • Most monocot plants.

  24. Flowering and Pollination • A plant is considered self-sterile if it requires pollen from another plant in order to set fruit. • Sterility is due to the protien composition of the cell of wall of pollen grains. • The protein sends a signal to the stigma indicating whether the pollen is from its own species or the same plant.

  25. Flowering and Pollination • Each pollen grain contains a tube cell and a generative cell. • When the pollen lands on the stigma, germination occurs.

  26. Flowering and Pollination • The tube cell forms a pollen tube that grows through the stigma and style. • The pollen tube enters the nucleus of the ovule by passing through the Micropyle

  27. Flowering and Pollination • The generative cell has produced two male gametes through the process of Mitosis.

  28. Flowering and Pollination • One gamete unites with the egg cell to form the Zygote, which form the embryo. • The other male gamete unites with the polar nucleus in the ovule to form the endosperm. • The endosperm the seeds food reserve for germination.

  29. Flowering and Pollination • The time between pollination and fertilization in most angiosperms is 24 to 48 hours. • Once fertilization has occurred, the ovule becomes the seed and the ovary becomes the fruit.

  30. Answer These Questions • 1. What is the time between pollination and fertilization. • 2. How many male gametes are produced through mitosis? • 3. What is the function of the gametes? • 4. Pollen enters the nucleus by passing through what opening? • 5. What causes sterility.

  31. Genetics and Heredity page 54 • The nucleus of a living cell contains Chromosomes. • Chromosomes contain information about the genetic makeup of the plant. • They transmit the information to offspring.

  32. Genetics and Heredity page 54 • Each plant species has the same number of chromosomes in all vegetative cells. • Sex cells have half the number of chromosomes as vegetative cells.

  33. Genetics and Heredity page 54 • Chromosomes are long, thread-like structures consisting of DNA (deoxyriboneucleic acid), RNA (ribonucleic acid), and consisting of proteins.

  34. Genetics and Heredity page 54 • Genes: organic bases located along DNA molecules. • The gene is the heredity unit of a plant.

  35. Answer these questions 1. Why do vegetative and reproductive cells have varying numbers of chromosomes? 2. Which type of material do chromosomes contain? 3. What does DNA stand for? 4. What does RNA stand for? 5. What is a gene?

  36. Genetics and Heredity page 55 • Chromosomes are usually found in pairs in each vegetative cell. • These are called Homologous Chromosomes. • They have the same genes affecting the same traits and are located at the same position along the chromosomes.

  37. Genetics and Heredity page 55 • Matching genes on Homologous Chromosomes are called Alleles. • Gene alleles always occur on the same Locus (location) along the pair of chromosomes. • Allelic genes can be dominant or recessive.

  38. Genetics and Heredity page 55 • A dominant gene causes a certain characteristic to be expressed. • A recessive gene causes the character to be expressed only if the alleles from both parents are recessive. • Dominant genes are represented by capital letters. • Recessive genes are represented by small letters.

  39. Genetics and Heredity page 56 • Meiosis controls the formation of egg and sperm cells. • As gametes are formed, the two alleles for a particular trait separate (segregate). • They segregate randomly so that each gamete receives one allele or the other.

  40. Genetics and Heredity page 56 • The allele composition of a plant is the Genotype.

  41. Genetics and Heredity page 56 • A common method of predicting the genotypes and phenotypes of offspring is the Punnett Square.

  42. Answer these questions 1. A common method for determining phenotypes and genotypes is the? 2. The allele composition of a plant is known as the? 3. What is a homologous chromosome? 4. Meiosis controls formation of which two sex cells? 5. Allelic chromosomes can be of two types, identify them.

  43. Plant Breeding page 57 • Read pages 57-60 • Plant Breeding: the process of selectively mating plants. • A basic type of plant breeding is Selection. • Selection is when two plants with desirable traits are chosen from a population and then reproduced.

  44. Plant Breeding page 58 • Hybridization: the crossing of two plants that have different genotypes. • Crossbreeding usually produces a plant that is more vigorous in growth that either of its two parents. • Hybrids do not pass many of their traits to their offspring, so parent stocks must be crossed each year to produce new seed.

  45. Plant Breeding page 58 • The production of hybrid seed is managed by production organizations. • Growers are under contract to grow the parent lines and make the hybrids. • Seed production fields must be isolated from other fields to prevent unwanted cross-pollination.

  46. Plant Breeding page 58 • When tassels begin to emerge, the female plants are detassled to prevent selt-pollination. • The wind then cross-pollinates the male parent with the female to produce hybrid seed.

  47. Plant Breeding page 59 Single Cross Inbred parent A x Inbred Parent B Single cross AxB • Inbreeding: the process of crossing two similar parents. • After inbreeding five to seven generations, certain phenotypes will be expressed. Three Way Cross Inbred parent A x Inbred Parent B Single Cross AxB x Unrelated Inbred C Three-way cross (AxB) x C

  48. Plant Breeding page 59 • Backcrossing: offspring are continously crossed with one of the parents.

  49. Biotechnology Techniques • Biotechnology: the management of biological systems for the benefit of humanity. • Biotech uses molecular biology and molecular genetics for developing plant breeding methods. • These include: tissue culture, protoplast fusion, embryo manipulation, recombinant DNA.

  50. Biotechnology Techniques • Micropropagation: the propagation (asexual) of plant cells or tissues in a closed container. • Cell culture: modifying the genetic makeup of the cell and then regenerating plants with desired traits.