Polygenic Inheritance

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Polygenic Inheritance

  1. 1. Polygenic Inheritance
  2. 2. What is polygenic inheritance? <ul><li>When a single characteristic (1 trait) is controlled by many sets of genes. </li></ul><ul><li>In humans, most traits that have anything to do with size, shape, and color are controlled by multiple sets of genes. </li></ul><ul><li>(e.g. AaBbCc – three sets for one trait) </li></ul><ul><li>What if you did the following cross? </li></ul><ul><li>AaBbCc x AaBbCc – each parent contribution? </li></ul><ul><li>3 dominant ( ABC ) / 3 recessive ( abc ) </li></ul><ul><li>2 dominant/1 recessive ( ABc, AbC, aBC ) </li></ul><ul><li>1 dominant/2 recessive ( Abc, aBc, abC ) </li></ul>
  3. 4. Record the number of Dominant Alleles in the Punnett Square
  4. 5. <ul><li>The number of dominant alleles determines how dark (or how big) the phenotype will be…AABBCC (very dark) aabbcc (very light) </li></ul><ul><li>Note the following Punnett Square… </li></ul>
  5. 10. Practice Problem <ul><li>The length of a stem is controlled by three genes – A_B_C_ </li></ul><ul><li>aabbcc – 4 cm tall </li></ul><ul><li>AABBCC – 16 cm tall </li></ul><ul><li>Each upper case allele represents an equal portion of the trait. </li></ul><ul><li>Suppose a 16 cm tall plant was crossed with a plant 4 cm tall. How tall is the F 1 ? </li></ul>
  6. 11. <ul><li>F 1 – 100% AaBbCc </li></ul><ul><li>Base height (4 cm) + # of upper case alleles ( 3 @ 2cm each) </li></ul><ul><li>4 + 6 = 10cm tall plants (AaBbCc) </li></ul>

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