What is probability?

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Punnett Squares Probability

• What is probability?

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Probability

• What is probability?
• The likelihood that a particular event will occur
• The principles of probability can be used to
  predict the outcomes of genetic crosses.

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Punnett Squares

• The gene combinations that might result from a
  genetic cross can be determined by drawing a
  diagram

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Tt X Tt Cross
Section 11-2
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Allele combinations

• Homozygous organisms that have two identical
  (same) alleles true-breeding for a particular
  trait
• TT
• tt
• Heterozygous organisms that have two different
  alleles hybrids for a particular trait
• Tt

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• Phenotype visible, physical characteristics
• Tall or short
• Genotype not visible, genetic makeup
• Homozygous or heterozygous

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Independent Assortment

• Does the gene that determines whether a seed is
  round or wrinkled in shape have anything to do
  with the gene for seed color?

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• NO!!!
• The alleles for seed shape and seed color in pea
  plants do not influence each others inheritance

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The Principle of Independent Assortment

• Genes for different traits can segregate
  independently during the formation of gametes.

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Summary of Mendels Principles

• Inheritance is determined by genes passed from
  parents to offspring
• Some forms of genes are dominant and others are
  recessive
• Each offspring has two copies of a gene
  (alleles), one from each parent because they are
  segregated during gamete formation
• The allele for different genes usually segregate
  independently of one another

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• What will happen if some alleles are neither
  dominant nor recessive?
• What will happen if some traits are controlled by
  more than one gene?

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Incomplete Dominance

• When one allele is not completely dominant over
  another
• For example 4 oclock plant

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Figure 11-11 Incomplete Dominance in Four OClock
Flowers
Section 11-3
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Figure 11-11 Incomplete Dominance in Four OClock
Flowers
Section 11-3
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Codominance

• Both alleles contribute to the phenotype of the
  organism
• For example roan