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Unit 3: Genetics Mendel and the Gene Idea Review
  1. Gregor Mendel experimented with peas,
  2. When Mendel mated two true-breeding varieties (the generation), all of the offspring (the generation) from this cross had flowers.
  3. Mendel proposed two principles of inheritance to explain his results.
  4. Law of .
    • "Heritable factors" (genes) have alternative versions called .
    • If the two alleles at a locus differ, the organism is , and the allele determines the organism's appearance, or .
    • The two alleles in meiosis, and rhe distribution of the segregated phenotypes can be calculated from a model called the square.
    • How can we determine the genotype of an organism with the dominant ? A testcross with an individual that is homozygous for the trait.
  5. Law of Independent .
    • Crossing true-breeding parents differing in two characters produces in the F1 generation heterozygous for both characters, and phenotypes in the F2 generation.
    • Each pair of alleles segregates and randomly during gamete formation, assuming they are on different ,
  6. Mendel's laws are based on probability, and obey rules of and .
    • In a cross, the probability of allele frequencies in the is the of the probabilities of allele frequencies in the .
    • In a cross, the probabilities of multiple allele combinations is the of the probabilities of the individual alleles.
  7. Extending Mendelian Genetics.
    • In dominance, the of the heterozygote and dominant homozygote are identical.
    • In dominance, the of is somewhere between the phenotypes of homozygotes. An example is the flower color of snapdragons.
    • In , two dominant alleles affect the phenotype. An example is the human blood group ABO, where phenotypes are determined by alleles.
    • Some traits exhibit inheritance which oftens shows variation.
    • In , a gene at one may alter the phenotypic expression of a gene at a second locus. An example is the mouse coat color.
  8. Inheritance in human families can be studied by analyzing a showing the inheritance of alleles across generations.
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