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Mendel and Meiosis

Mendel and Meiosis. Gregor Mendel. Heredity is the passing of characteristics from parents to offspring. Genetics is the study of heredity or how those traits are inherited.

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Mendel and Meiosis

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  1. Mendel and Meiosis

  2. Gregor Mendel • Heredity is the passing of characteristics from parents to offspring. • Genetics is the study of heredity or how those traits are inherited. • Gregor Mendel was the first person to succeed in predicting how traits were inherited thus he became known as the Father of Genetics.

  3. Gregor Mendel • Gregor Mendel is best known for his study of pea plants. • He used pea plants because they have 2 distinct sex cells called gametes. • Mendel pollinated the flowers himself by transferring the male pollen to the stigma of the flower (pollination).

  4. Pollen

  5. Uniting of the male and female gametes is called fertilization.

  6. Mendel cross-pollinated pea plants in order to study the various traits: Dominant: the trait that was observed Recessive: the trait that disappeared.

  7. Crossing traits • Purebred: a cross between plants with identical traits. • Hybrid: a cross between plants with different traits like tall and short. • Mendel’s first cross he called a monohybrid cross. (Mono means one) • Later Mendel began crossing plants with 2 traits. These crossed were called dihybrid crosses. • Testcross: Breeding an individual of unknown genotype to a homozygous recessive individual to reveal the unknown genotype

  8. Parent generation Parents Filial (son or daughter) generation Children 2nd Filial generation Grandchildren

  9. Genotypes and Phenotypes?? • Phenotype – the way that the organism looks and behaves. Pheno (physical) type (model) • Genotypes – the combination of genes in the organism. Gen (birth) type (model)

  10. Genotypes and Phenotypes • Phenotype • Genotype

  11. Genotypes and Phenotypes • Homozygous dominant: Homo (same) • Homozygous recessive: • Heterozyous: Hetero (different) • t • t • t • Alleles • T • T • T

  12. Mendel’s Laws of Inheritance • Law of segregation: the 2 genes for each trait will segregate during the formation of the gametes. • t • T

  13. Mendel’s Laws of Inheritance • Law of independent assortment: Each trait (or gene) is inherited independently of the other traits. • In other words, all blondes do not have blue eyes.

  14. Punnet Squares • In 1905, Reginal Punnet, an English biologist, devised a shorthand way of predicting the outcomes of the various crosses. • These are called Punnet squares.

  15. Monohybrid crosses BB: White bb: Black Genotypes Phenotypes BB: 1…25% Bb: 2…50% bb: 1…25% White: 3…75% (BB and Bb) black: 1…25%

  16. Dihybrid crosses

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