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INTRO TO GENETICS

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					INTRO TO GENETICS
                       History
 Native Americans
   Domestication of wolf
   Developing corn & potatoes
 Aristotle
   Blood contains hereditary
    material
      “blood relatives”, “bloodline”
       “Blending Hypothesis”
 “Renaissance” (17th century)
 Parents traits (characteristics) are blended
  together in their offspring.
 Example: A tall mom and short dad will
  produced a child with medium height.
            Gregor Mendel
 Austrian monk (19th century)
 Other interests:
   Math, biology, physics
   Pea breeder
 “Father of Genetics"
     Peas: the perfect specimen
   Produce many offspring
   Short life cycle
   Easy to control the experiment
   Easily identified traits:
                   Pea Biology
 Plant reproduction
   Pollen produced in stamen
       Carries sperm
   Egg contained in the pistil
       Holds the egg
   Pollen grain lands on pistil
    and produces a pollen
    tube.
       Sperm travels through tube.
       Sperm fertilizes the egg.
Method of Self-fertilization
                Selective Breeding
 Parent Generation
    “Purebred” (self-fertilized)
     parents.
 F1 Generation
    “Hybrid” offspring“
    All possess traits of one
     parent.
 F2 Generation
    Self-fertilized
    3 of 4 with one parent trait.
    1 of 4 with the other parent
     trait
          Mendel’s Hypothesis
 Each trait is controlled by a gene.
 Two or more alternative forms of a gene (ex. tall &
  short). These forms are called “alleles”.
 Each trait is the result of a pair of alleles being
  expressed.
    Each allele being located on different copies of a chromosome
    Example: Tall / tall; tall / short; short / short
          Law of Dominance
 One allele is dominant over the other
   Tall (T) is the dominant allele
   Short (t) is the recessive allele
 Pure dominant (T / T) and hybrid (T / t) will
  produce tall plants.
 Only pure recessive (t / t) will produce
  short plants.
                   Terminology
 Genotype – combination of alleles
   Ex.: “T / t”
 Phenotype – expression of the allele pair.
   Ex.: “tall”
 Homozygous – allele of pair is the same
   Ex.: “t / t”
 Heterozygous – alleles of pair are different
   Ex.: “T / t”
          Law of Segregation
 Pairs of alleles separate when “gametes”
  (sex cells) are produced.
   Example: Hybrids (T / t) will have gametes
    with either “T” allele or “t” allele.
 Alleles will pair up again during
  fertilization.
   Ex.: “T” from sperm and “t” from egg will
    produce a “T / t” allele pair.
           Punnett Square
 Predicts result between parents.
Monohybrid Cross
Law of Independent Assortment
 Genes for different
 traits are inherited
 independently of
 each other
   Ex.: Alleles for
    height will not
    influence the alleles
    for seed color or
    seed shape
           Dihybrid Cross
 Two genes, each that are heterozygous.

				
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