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Fundamentals of Genetics

Fundamentals of Genetics. Gregor Mendel. Gregor Mendel. Was a Monk in Brunn, Austria He entered the University of Vienna and studied math and science His research on pea plants helped us understand heredity- the transmission of characteristics from parent to offspring. Heredity.

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Fundamentals of Genetics

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  1. Fundamentals of Genetics Gregor Mendel

  2. Gregor Mendel • Was a Monk in Brunn, Austria • He entered the University of Vienna and studied math and science • His research on pea plants helped us understand heredity- the transmission of characteristics from parent to offspring

  3. Heredity • People always knew that children looked like their parents… but they didn’t know why this was. • Most people believed that children were a “blending” of their parents • People also didn’t understand why siblings looked alike, but didn’t look the same

  4. Mendel’s Experiments • While living at the monastery, Mendel studied pea plants • He selectively bred the plants and recorded the appearance of the offspring

  5. What traits did Mendel observe? • Mendel observed seven characteristics of pea plants • Height: Long or Short Stems • Flower Position: Axial or Terminal • Pod Color: Green or Yellow • Pod Appearance: Inflated or Constricted • Seed Color: Yellow or Green • Seed Texture: Smooth or Wrinkled • Flower Color: White or Purple

  6. How do you breed plants? • Mendel was able to accurately record his results by carefully controlling how the plants were pollinated • Flowers have reproductive parts • Anthers: Male • Pollen: Sperm • Stigma: Female • Self Pollination • Cross Pollination

  7. Flower Parts

  8. Pea Plants Mendel’s Crosses Pea Plants normally reproduce through self-pollination By removing the anthers and manually transferring the pollen from another plant onto the stigma, you can induce cross-pollination

  9. Genetic Crosses • Mendel studied 7 characteristics and each contrasting trait (tall vs short) in pea plants. • The plants he used were Pure, meaning they always produce offspring with that trait. (ex. Purple flowers always produced purple flower offspring). • Mendel had 14 pure strains of plants (one for each characteristic and its contrast) = P generation (Parental)

  10. Genetic Crosses • Mendel crossed his pure pea plants • According to the conventional wisdom of the time, we would expect to have a “blending” of characteristics • Mendel crossed a Tall Plant with a Short Plant (P generation). The resulting offspring are called the F1 generation. (First Filial Generation) • We might expect to get all medium height offspring or about 50% tall and 50% short

  11. However…. • All of the offspring in the F1 generation were tall! • This goes against our notion of “blending” • Why were all the plants tall? What happened to the short trait?

  12. All of the F1 plants were self-pollinated to produce the F2 generation (second filial generation) • We would expect them to be all tall as well. • However, Mendel found that the short trait reappeared. • 75% of the offspring were tall • 25% of the offspring were short • This 3:1 Ratio was found in the F2 Generation of ALL of Mendel’s Crosses

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