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Genetics in Agricultural Breeding Programs


Genetics in Agricultural Breeding Programs ... methods vary widely by the type of animal Artificial vaginas are ... Cross-Pollination in Plants Method used to select ... – PowerPoint PPT presentation

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Title: Genetics in Agricultural Breeding Programs

Genetics in Agricultural Breeding Programs
Natural Selection
  • Mechanism for evolution in natural populations
  • Organisms with best traits suited to the
    environmental factors affecting a population are
    most likely to survive and reproduce.
  • Results in the inheritance of the same
    well-suited traits
  • Important traits in natural selection-disease
    resistance, size, color pattern/camouflage, etc.

Natural Selection
  • Types of Natural Selection
  • Stabilizing selection
  • Directional selection
  • Disruptive selection

Stabilizing Selection
  • Individuals with the average or norm for a trait
    have an advantage over other forms of the trait
  • Example gray moths (norm) are favored over
    black and white moths

Directional Selection
  • Individuals with one extreme or less common
    version of a trait are favored over other forms
    of the trait.
  • Example Black moths are favored over gray or
    white moths

Disruptive Selection
  • Multiple extremes or alternative forms of a trait
    are favored over the norm
  • Example Black moths and white moths are favored
    over gray moths

Selective Breeding
  • Method of breeding plants and animals utilized in
    agriscience to produce offspring that possess
    certain characteristics desirable to
  • Utilized for generations-produced the first
    domestic animals in early civilizations

Selective Breeding
  • Used to select for a variety of traits including
  • Muscling/Size
  • Fat content
  • Breeding Capability
  • Color
  • Speed/Agility
  • Temperament
  • Milk Production

Selective Breeding
  • Methods for selective breeding
  • Artificial insemination
  • Pen/field breeding
  • Isolation Breeding-inbreeding
  • Mechanical pollination of plants
  • Hybridization of plants and animals

Selective Breeding
  • Selective breeding is accomplished much quicker
    in plants than animals due to growth rates and
    ease of propagation/production

Selective Breeding Techniques
  • Objective Summarize the process and purpose of
    selective breeding techniques

Techniques in Animals
  • Progeny testing is used to determine the value of
    male livestock by analyzing the transmission of
    traits to offspring and its breeding potential
  • Artificial insemination has proven to have the
    greatest impact on animal breeding since the
    first domestication of livestock.

Artificial Insemination
  • Semen is collected from male individuals
    methods vary widely by the type of animal
  • Artificial vaginas are used for larger mammals.
  • Semen is checked for viability and flash frozen
    in specialized straws.
  • Straws should be placed in storage tanks filled
    with liquid nitrogen, till use.
  • Semen stored under proper conditions has proven
    viable decades later (-320ºF)
  • Female is treated with prostaglandin (hormone) to
    induce estrus or heat
  • Semen straws are immediately thawed in water
    (99ºF) and soon after inserted into the mother
    using a specialized release gun.

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

  • Method of removing eggs from a mother for
    fertilization under laboratory conditions.
  • 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 surrogate mothers or
    frozen for later use
  • Offers the most control and requires the least
    amount of semen.

Birth Through Surrogate Mothers
  • Hormones are used to cause the female to
    superovulate (produce a large number of eggs).
  • Original mother undergoes artificial insemination
  • Fertilized eggs are removed by a process called
    FLUSHING to be placed in other female animals for

Cross-Pollination in Plants
  • Method used to select particular parents for the
    production of seed in plants.
  • Process
  • Plants possessing desirable characteristics are
    selected and carefully monitored
  • Pollen can be gathered from male plants (or
    flowers) months or in some cases, years in
    advance and refrigerated for storage
  • Flowers on the female part must be covered prior
    to opening, and if capable of self-pollination,
    must have the stamens removed.
  • 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.

Selecting Plants and Animals for Breeding
Observe Patterns of Heredity
  • The occurrence of genetic disorders in offspring
    or parents is an indicator that the parent may
    have a recessive gene for the disorder
  • Though genetic recombination is random, some
    animals are more likely to transmit genes than
  • Keeping careful breeding records improves

Select Animals Carefully
  • Along with a good genetic background, animals
    used in selective breeding should be
  • Healthy-old injuries or illnesses are not a
    factor unless they are a result of genetic
    propensities or impair breeding capabilities
  • Carefully monitored-nutrition levels, pests and
    stress can all reduce breeding viability. Some
    very good specimens are completely isolated.

Select Animals Carefully
  • Hybrids should be avoided, since traits expressed
    in the organism are rarely transmitted to
  • The process of inbreeding isolates genes for only
    a single generation, as many are recessive.

Carefully Plan Breeding Crosses
  • Plants can be crossed not only within species
    (interspecific), but also within genus
    (intergeneric), and even, in rate cases family
  • Animals are usually limited to crosses within the
    same species

Methods for Producing Selective Breeding Programs
  • Crossing organisms that are genetically related
  • Crossing two plants to produce an f1 generation,
    then crossing two of the f1 offspring to create
    an f2 generation

  • Crossing offspring from a cross with one of the
    previous parents, or a similar organism, to
    maximize the expression of certain traits.
  • Often used after intergeneric crosses to produce
    offspring that possess more characteristics from
    one genus.
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