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Chapter 11 Introduction to Genetics

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Chapter 11 Introduction to Genetics Powered By Docstoc
					      Chapter 11
Introduction to Genetics
        Biology
       Mrs. Craun
               Gregor Mendel
• Born in 1822, died in 1884
• Austrian Monk
• Studied Science and Math at the University of
  Vienna
• Tended a monastery Garden and taught high
  school
• Considered the “Grandfather of Genetics”
   How did Mendel
   study genetics?


• By trade, Mendel was a mathematician and studied
  statistics.
• As part of his duties, he took care of the monastery
  garden.
• He noticed that offspring tended to have the same
  characteristics as the parents
  – Remember…no one knew anything about DNA in the
    mid-1800’s!!
    What traits did Mendel study in
              pea plants?
•   Seed shape
•   Seed color
•   Seed coat color
•   Pod shape
•   Pod color
•   Flower position
•   Plant height
How did Mendel study genetics?


   Mendel first looked at true-breeding
   plants, and then cross-pollinated them
              creating hybrids
            Terms to Define
• true-breeding:

• cross-pollination:

• hybrid:
Mendel’s Breeding Program
Mendel’s Breeding Program
             • P generation: parent
               generation
  Hybrid Cross
• Did Mendel see a
  combination of
  parental traits in
  hybrid offspring?



  – offspring = F1 generation
     • F1: filial generation
    Mendel’s Conclusions from the
          First Experiment
•   Inheritance must be determined by factors
    passed from one generation to the next
    –   We now know these as the genes found on your
        chromosomes
•   Principle of Dominance
    –   Mendel realized some traits are dominant and
        others are recessive
    –   Dominant alleles “overpower” recessive alleles,
        so only the dominant characteristics are seen
        when they combine.
      Mendel’s First Cross:
only one parent’s traits were seen
        in F1 generation
   Mendel’s Second Experiment
• Mendel wondered if the recessive alleles
  were still present(perhaps just hidden?).
• He let his F1 generation plants self-pollinate
  – self-pollination:
   Mendel’s Second Experiment
• F1 generation self-
  pollinates 
         F2 generation
• Notice that the
  recessive trait (white
  flowers) shows up
  again although the
  parent was pink
    Mendel’s Conclusion from Second
              Experiment
• Remember: Organisms
  have two copies of each
  gene in their cells- one
  from the mom and one
  from the dad
• During meiosis these two
  copies are duplicated and
  then separated, so that
  each gamete has only one
  copy of the
  gene/chromosome.
Mendel’s Conclusion from Second
          Experiment
   Mendel’s Conclusion from Second
             Experiment
principle of segregation: two copies of a gene
   separate, or segregate during the formation
                 of egg and sperm
    …we now know this happens through the
                process of meiosis
          Mendel’s Principles
1- dominance and recessivness: two forms for
   every trait; one form masks (dominant) the other
   (recessive)
2- segregation: genes separate during the formation
   of egg and sperm
3- independent assortment: no two genes are
   connected and separate independently of each
   other during formation of egg and sperm
       - no two traits are connected

				
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