Heredity and Reproduction

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Chapter 3

• Heredity and Reproduction

Original Power Point Created by Chris
Clemmons Modified by Georgia Agricultural
Education Curriculum Office June 2002
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Heredity and Reproduction

• A plant or animal is only as developed as its
  genetic components.
• An animal or plant receives its characteristics
  from its parents.
• Scientists are continously searching for improved
  crop and animal varieties through Selective
  Breeding.

Read pages 43-45
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Heredity and Reproductionpage 43

• The first major breakthrough in plant breeding
  occurred in the 1930s 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?

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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.

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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

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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?

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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?

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Flowering and Pollination

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

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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.

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Flowering and Pollination

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

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Flowering and Pollination

• An incomplete flower lacks one or more of the
  before mentioned structures.

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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.

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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?

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Flowering and Pollination

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

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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.

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Flowering and Pollination

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

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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.

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Flowering and Pollination

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

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Flowering and Pollination

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

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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.

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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.

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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.

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Flowering and Pollination

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

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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.

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Flowering and Pollination

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

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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

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Flowering and Pollination

• The generative cell has produced two male gametes
  through the process of Mitosis.

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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.

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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.

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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.

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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.

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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.

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Genetics and Heredity page 54

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

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Genetics and Heredity page 54

• Genes organic bases located along DNA molecules.
  
• The gene is the heredity unit of a plant.

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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?

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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.

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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.

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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.

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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.

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Genetics and Heredity page 56

• The allele composition of a plant is the
  Genotype.

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Genetics and Heredity page 56

• A common method of predicting the genotypes and
  phenotypes of offspring is the Punnett Square.

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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.

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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.

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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.

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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.

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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.

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Plant Breeding page 59

• Inbreeding the process of crossing two similar
  parents.
• After inbreeding five to seven generations,
  certain phenotypes will be expressed.

Single Cross Inbred parent A x Inbred Parent
B Single cross AxB
Three Way Cross Inbred parent A x Inbred Parent
B Single Cross AxB x Unrelated Inbred C Three-way
cross (AxB) x C
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Plant Breeding page 59

• Backcrossing offspring are continously crossed
  with one of the parents.

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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.

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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.

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Biotechnology Techniques

• Microinjection the mechanical insertion of
  genetic material into a single, living cell.
• Cell walls can be dissolved using enzymes.
• This exposes the cells protoplast.
• This allows the genetic makeup of different
  plants to be fused together.

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Biotechnology Techniques

• Recombinant DNA or genetic engineering involve
• 1. Gene splicing
• 2. Replication
• 3. Transfer of genes to other organisms
• Transgenic organisms would carry in their cells a
  foreign gene.

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Biotechnology Techniques

• 1. Starts with cutting gene with an enzyme.
• 2. The sliced gene is then removed and inserted
  into a circular DNA molecules called plasmids
  found in bacteria.

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Biotechnology Techniques

• 3. An enzyme is used to seal the spliced ends.
• 4. The DNA plasmid is inserted into a cell
  selected for alteration.
• 5. The result is a new sequence of DNA.

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Answer these Questions

• 1. What three items does genetic engineering
  include?
• 2. What is micro-injection?
• 3. What is cell culture?
• 4. What is biotechnology?
• 5. Describe the process of gene splicing?