Polygenic Inheritance
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Polygenic Inheritance

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    Polygenic Inheritance Polygenic Inheritance Presentation Transcript

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