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Variations of Mendelian Genetics

  1. In short horn cattle, a red bull (RR) is crossed with a white cow (rr). The offspring are roan, intermingled red and white hairs.
    1. What do we call this variation of Mendelian genetics?
    2. How would a rancher maintain a herd of roan cattle?
  2. The coat color in cattle1 is described by the following genetic characteristics:
    • The gene for black (Rb) is dominant to the gene for red (R).
    • The gene for black (Rb) and the gene for white (r) are codominant. Therefore, an individual with one gene for black and one gene for white will be black-roan (intermingled black and white hairs).
    • The gene for red (R) and the gene for white (r) are also codominant, producing the red-roan when these two genes are present.
    • An individual with two genes for white (r) will be white.
     

    Describe the monohybrid cross using a Punnett square AND give the phenotypic ratio for these crosses:

    1. A homozygous black cow with a homozygous red bull.
    2. A homozygous black cow with a homozygous white bull.
    3. A homozygous red cow with a homozygous white bull.
  3. The storage roots of radishes may be long, round or oval. Using the data below from a series of experiments, show how root shape is inherited in radishes.
    • Crosses between long and oval produced 159 long and 156 oval.
    • Crosses between round and oval produced 199 round and 203 oval.
    • Crosses between long and round produced 576 oval.
    • Crosses between oval and oval produced 121 long, 243 oval and 156 round.

References:

1. "Color Pattern Inheritance in Beef Cattle. Dr. Stanley R. McPeake. University of Arkansas Cooperative Extension Service. 2002. FSA3067-PD-6-01N. Online. http://www.uaex.edu"