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					Inheritance




  Chapter 7
Inheritance: the way genes are passed down.
                               • If a father
                                 doesn’t have
                                 a leg does
                                 that mean his
                                 children will
                                 be born with
                                 out a leg????
Hundreds of years ago people knew that somehow
certain traits would be passed on to their children.
Gregor Mendel was the first to predict the outcome
of inheritance. The study of inheritance is Genetics.
• Mendel did
  several
  different
  experiments
  on pea plant.
• This is an
  example of
  wrinkled and
  smooth seeds.
Genes and Alleles
          • A gene is a specific
            piece of DNA.
          • You have two genes
            that code for the
            same thing (ex.
            Height). Each of
            those two genes is
            called an allele.
          • So if something had
            the genes Aa one
            allele would be “A”
            the other would be
            “a”).
Why two alleles for every gene?
                • Because organisms get
                  2 sets of chromosomes
                  ……….one from the
                  mother and one from
                  the father.
Phenotype
     • Is the physical
       characteristics of the
       trait.
     • In most cases it is
       what we can “see”.
     • Example: Freckles,
       dimples, attached
       earlobes etc.
                Genotype
• Is the actual alleles that make up the trait.
• In most all cases this is represented by 2
  letters.
• Example: AA, Aa, aa
Dominant
       – A dominant trait is a trait
          that covers or hides the
          other trait of an allele.
    • For example, dark colors in hair
      usually overshadow the other
      allele.
    • In this class Dominant will
      always be represented with a
      capital letter.
    • Example: Say “D” is the allele
      for black hair and “d” is the
      allele for blond. The if an
      animal had Dd then it would
      have black hair.
Recessive
     • A recessive trait is the
       trait that is hidden by
       the dominant trait.
     • In an animal with Dd
       for hair color the
       recessive allele is “d”.
     • The animal carries a
       gene for blond hair but
       you can’t tell by
       looking at it.
Heterozygous
      • This is the term given
        two different alleles.
      • For example, Aa is
        heterozygous.
      • It may contain one
        gene for brown
        eyes(A) from the
        mother and one gene
        for blue(a) eyes from
        the father.
Homozygous
     • This is the term given
       to the two same
       alleles.
     • For example, AA or aa
     • A person may contain
       2 genes for -brown
       eyes – one from each
       parent (AA) or 2 for
       blue (aa).

				
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