Mendelian Inheritance and Phenotypic Traits

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Mendelian Inheritance and Phenotypic Traits

• March 19, 2008

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Gregor Mendel

• 19th century Austrian monk and scientist.
• Was first to clearly explain fundamental patterns
  of inheritance.
• Carried out experiments using pea plants.

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Phenotype vs. Genotype

• Phenotype physical appearance.
• Genotype genetic sequence.
• In most instance a genotype of an organism
  determines its phenotype.

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Genes and Alleles

• Gene a discrete physical unit of inheritance
  coded by DNA. A gene often refers to an
  inheritable trait.
• Example a gene for eye color, or a gene for wing
  length.
• Allele alternative form of a gene. May be two
  or more alleles for each trait or gene.

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Alleles Dominant and Recessive

• Dominant alleles will mask or hide the recessive
  allele.
• Recessive alleles only will be expressed in the
  phenotype when paired with another recessive
  allele.
• EXAMPLE

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Generations

• P or parental generation.
• F1 or first filial generation.
• F2 or second filial generation.

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Punnett Square
Monohybrid cross- involving one pair of gene
traits
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Dihybrid Cross
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Sex-linked Cross
Drosophila eye-color example (p. 114)