Applied Genetics in Agriculture and Agriscience

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Applied Genetics in Agriculture and Agriscience

• Competency 16.00

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Sexual Reproduction Terms

• Fertilization-the union of haploid cells in both
  plants and animals
• Occurs in the ovary of plants and the uterus of
  animals

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Sexual Reproduction Terms

• Embryo-a fertilized egg/ovule that will grow to
  produce new offspring

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Sexual Reproduction Terms

• Ovary-organ responsible for the production of
  eggs/ova in plants and animals

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Sexual Reproduction in Plants
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Pollination

• The transfer of male pollen to the female
  reproductive organs
• Pollination must occur before fertilization
• Removal of the stamen is the first step in
  mechanical cross pollination

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Germination

• The initial vegetative growth of a seed

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The Stamen

• Male reproductive parts
• Anther-top of the male flower, contains pollen
• Filament-long slender stock on which the anther
  sits

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The Stamen
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The Pistil

• Female Reproductive Parts
• Stigma-the swollen end of the pistil, sticky to
  receive the pollen
• Style-stalk connecting the stigma to the
  ovary-pollen on the stigma forms long tubes
  through the style
• Ovary-produces and stores the ova (seeds), and
  protects seeds during development
• 1 ovum1 seed and 1 ovary1 fruit

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The Pistil
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Types of Flowers

• Complete-have all the parts of a flower (Stamen,
  Pistil, Sepals, Petals)
• Incomplete-missing any part of the flower

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Types of Flowers

• Perfect-have all the reproductive parts of a
  flower (Stamen and Pistil)
• Imperfect-missing any reproductive part of the
  flower

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Cross Pollination

• The method used to select particular parents for
  the production of seeds in plants.

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Cross Pollination-Step 1

• Plants possessing desirable characteristics are
  selected and carefully monitored.

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Cross Pollination-Step 2

• Pollen can be gathered from male plants (or
  flowers) or in some cases, years in advance and
  refrigerated for storage.

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Cross Pollination-Step 3

• Flowers on the female plant must be covered prior
  to opening, and if capable of self-pollination,
  must have the stamens removed.

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Cross Pollination-Step 4

• Once the female flowers open, pollen from the
  male should be placed on the stigma, and the
  flower covered again.
• Record keeping is critical in crossing plants.

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Asexual Reproduction in Plants
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Stem Cuttings

• Section of the stem or branch is cut, treated
  with a rooting hormone, and placed in soil or
  water to encourage the development of roots.

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Stem Cuttings

• Should always be taken just above a node for best
  rooting.
• Most common method of asexual propagation, used
  for both woody and herbaceous plants.
• Can also do leaf and root cuttings.

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Air Layering

• Section of the stem or branch has the bark
  removed or slightly damaged and a rooting hormone
  applied.
• The area is then covered with soil, wrapped in
  cellophane until well developed roots can be seen
  through the plastic.

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Air Layering

• The branch or stem is cut below the roots only
  after roots have fully developed.

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Tissue Culture

• Common method of asexual production utilizing
  extremely small amounts of plant material
• Often uses meristem tips-the tip of a branch
  where most active growth is occurring

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Tissue Culture

• Tissue is removed from the plant, sterilized and
  cultured on agar in aseptic conditions.
• Meristematic tissue develops shoots, is
  transferred to another media to develop
  adventitious roots, is hardened off, and finally
  transferred to soil.

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Division

• Method of plant propagation conducted by
  physically separating a plant into several
  smaller plantlets.
• Often used for grasses and lilies
• A variation is the production of non-tunicate
  bulbs from scales (each scale must contain a part
  of the bottom of the bulb, the basal plate.

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Grafting

• The process of removing plant material from one
  plant for incorporation into another plant
• Often used with fruit trees to create dwarf
  varieties

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Grafting-2 Parts

• Scion-the top portion of a graph that will form
  the main part of the plant.
• Rootstock-the bottom portion of the graft that
  usually controls growth habit (size of the plant)
  but produces no vegetation

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Grafting-2 Parts
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Budding

• Related to grafting
• Instead of using a scion, exchange of plant
  material is accomplished with a single bud

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Grafting and Budding

• SCION AND ROOTSTOCK REMAIN GENETICALLY DISTINCT
  EVEN AFTER COMBINATION

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Sexual Reproduction in Animals
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Fertilization

• Occurs internally in most animals-all mammals
• Some fish and insects are exceptions

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Haploid Cells

• Male cells are spermatazoa (sperm)
• Released in semen to aid in the process of
  fertilization

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Haploid Cells

• Female cells are eggs
• Produced in the ovary
• Fertilized and developed within the uterus
• Females release eggs on a cycle (menstrual cycle)
  that varies in time length according to species

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Selective Breeding Techniques in Animals
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Progeny Testing

• Determines the value of male livestock by
  analyzing the transmission of traits to offspring
  and its breeding potential

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Artificial Insemination

• Proven to have the greatest impact on animal
  breeding since the first domestication of
  livestock

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AI Process

• Semen is collected from male individuals-methods
  vary widely by the type of animal
• Artificial vaginas are used for larger mammals

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AI Process

• Semen is checked for viability and flash frozen
  in specialized straws
• Straws should be placed in storage tanks filled
  with liquid nitrogen until use
• Semen stored under proper conditions has proven
  viable decades later (-320 degrees F)

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AI Process

• Female is treated with prostaglandin (hormone) to
  induce estrus or heat

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AI Process

• Semen straws are immediately thawed in water (99
  degrees F) and soon after inserted into the
  mother using a specialized release gun.

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AI Process
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Sperm Sexing

• Utilizes a cytometer cell sorter to separate male
  sperm from female sperm
• Sperm with X chromosomes (female) weigh more
  (contain more DNA) than those with a Y and can be
  dyed and separated because they absorb more dye

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In-vitro Fertilization

• A large number of eggs are collected from the
  ovaries of an outstanding female and fertilized
  in Petri dishes under laboratory conditions
• Embryos can be inserted into a surrogate or
  frozen
• Offers the most control and requires the least
  amount of semen.

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Surrogacy

• Hormones are used to cause the female to
  superovulate (produce a large number of eggs)

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Surrogacy

• Original mother undergoes artificial insemination
• Fertilized eggs are removed by a process called
  FLUSHING to be placed in other female animals for
  development.

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Cloning
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Cloning

• Allows rapid production of large numbers of
  genetically identical organisms
• Agriculturists can quickly disseminate
  outstanding traits

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Cloning

• Clones are genetically identical (the exact same
  DNA)
• Any genetic differences results from
  environmental factors-disease, nutrition,
  physical injuries, etc.

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Plant Cloning

• Most often utilized for the culture of plants
• Cheaper, easier process
• Less political opposition
• The ability to differentiate is more in plants
  than animals.

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Plant Cloning

• Tissue culture-the production of plants from
  small amounts of vegetative materials in an
  in-vitro environment
• An increasingly popular and effective method of
  plant production

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Animal Cloning

• Animals are cloned almost exclusively by the
  division of embryos
• In recent years, diploid cells have been cloned,
  but the process is extremely expensive and
  results in high losses

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Animal Cloning

• Dolly the sheep was produced from mammary gland
  cells in a sheep

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Transgenic Organisms
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Transgenic Organisms

• Can potentially be created using genes from any
  living organism
• The trick is finding a method for insertion and
  successful expression

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Transgenic Organisms

• Genetically modified organisms transmit inserted
  genes at the same rate as naturally occurring
  genes
• Once a gene is inserted, it can be passed on
  through sexual reproduction

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Creating a Transgenic Organism
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Step 1

• Develop a purpose/goal
• The transmission of genes from one organism to
  another is both expensive and potentially
  dangerous, expectations for work should be laid
  out carefully.

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Step 2

• DNA must be extracted from the target organism
  and the specific gene to be introduced isolated
  utilizing restriction enzymes

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Step 3

• Vectors are used for the transmission of target
  genes
• Viruses make good vectors, as they often insert
  DNA into organisms they affect
• Plasmids are the viruses most used
• Plasmids can store large strands of DNA or even
  one or more chromosomes

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Step 3-continued

• Some vectors can transmit genes simply through
  contact with target cells in a liquid solution or
  by microinjection.

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Step 4

• Isolated DNA is inserted into the new organism by
• Micromanipulation
• Biolistics

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Micromanipulation

• The isolated DNA segment is injected into a
  target cell utilizing a microscopic syringe under
  high magnification
• Most common form of gene insertion

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Biolistics

• Used a gene gun to fire gold plated .22 caliber
  shells that have been covered with the target
  gene into a mass of plant cells
• Most often used for plants
• Cell mortality is high