Fundamentals of Genetics

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Fundamentals of Genetics

• Ch.9

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(9-1) Genetics

• Field of Bio focused on how characteristics are
  passed from parent to offspring (heredity)
• Gregor Mendel
• Father of Genetics

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Mendels Peas

• Studied 7 characteristics (heritable features) of
  peas
• Ex plant height
• Each characteristic had 2
• different traits
• Ex long or short stems

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Mendels Experiments

• Started w/ 2 pure plant groups for a particular
  characteristic
• P generation
• Cross-pollinated (sexual reprod.) those plants to
  produce the next generation
• F1 generation

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Experiments (cont.)

• Allowed F1 plants to self-pollinate (asexual) to
  produce the next generation
• F2 generation

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Mendels Results

• F1 always showed only 1 of the 2 traits
• Dominant factor masked other trait
• F2 always showed a 31 ratio b/w the 2 traits
• Recessive factor factor being masked

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Mendels Laws

1. Segregation
2. Independent Assortment

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Law of Segregation

• A pair of factors separate during gamete (sex
  cell) formation

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Law of Independent Assortment

• Factors for different characteristics are
  distributed to gametes independently
• Ex not all blue eyed people have blond hair

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Molecular Genetics

• Study of the structure function of chromo.s
  genes
• Allele alternate form of a gene
• Dominant capital letter (B)
• Recessive lower case letter (b)

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(9-2) Genetic Crosses

• Genotype genetic makeup
• BB, Bb, bb
• Phenotype physical appearance
• Not all alleles shown
• BB black, Bb black, bb white

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Genotype Vocab

• Homozygous (purebred) same alleles for the
  characteristic
• BB ho/go dominant
• bb ho/go recessive
• Heterozygous (Hybrid) different alleles for the
  characteristic
• Bb

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Probability

• Likelihood that a specific event will occur
• Determined by a Punnett square

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Punnett Squares

• Monohybrid Cross 1 characteristic
• Dihybrid Cross 2
• Trihybrid Cross 3

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Testcross

• Dominant phenotype, but what genotype?
• Unknown genotype crossed w/ ho/go recessive

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Complications

• Incomplete dominance
• Codominance
• Multiple alleles
• Pleiotropy
• Polygenic Inheritance
• Epistasis

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Incomplete Dominance

• Both alleles blend to make phenotype
• Ex
• red (RR) x white (rr)
• pink (Rr)

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Codominance

• Both alleles expressed in a he/go offspring
• No blending!
• Ex red (RR) x white (rr) roan (Rr)
• Roan red white

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Multiple-alleles

• Traits controlled by 3 or more alleles of the
  same gene
• Blood groups (A, B, O)

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Pleiotropy

• 1 gene affects many characters
• Hemoglobin sickling allele

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Polygenic Traits

• 1 trait determined by multiple genes
• Skin color

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Epistasis

• Expression of 1 gene depends on another
• Hair color
• albinism genes