Chapter 3 by O3L09H

VIEWS: 2 PAGES: 55

									Chapter 3


Heredity and Reproduction




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Heredity and Reproduction
   A plant or animal is only   Read pages 43-45
    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.
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Heredity and Reproduction
page 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?            3
Heredity and Reproduction
page 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 Reproduction
page 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               5
Chapter 3 Objectives
page 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?     13
Flowering and Pollination

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




                                            14
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.                18
    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
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    occur.
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. 22
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.            24
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
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    for germination.
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.      29
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.                           38
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.




                                            41
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
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  types, identify them.
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.                                   44
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                Single Cross
                         Inbred parent A x Inbred Parent B
    process of                   Single cross AxB
    crossing two
    similar parents.
   After inbreeding
    five to seven               Three Way Cross
                        Inbred parent A x Inbred Parent B
    generations,     Single Cross AxB x Unrelated Inbred C
    certain                Three-way cross (AxB) x C
    phenotypes will
    be expressed.
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Plant Breeding page 59

   Backcrossing: offspring are continously
    crossed with one of the parents.




                                          48
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.                        49
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.


                                               50
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?

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