Experiment Three: The Inheritance of Plant Color
Green, Yellow-Green, and Purple (Anthocyanin Present)
There are two genes that are responsible for plant color in Brassica rapa. Anthocyanin, purple pigment (ANL), and no purple pigment (anl) are alleles of one gene. Green (YGR) and yellow-green (ygr) are alleles of a second gene. In the homozygous recessive condition of the latter, ygr/ygr, plants have yellow-green color in cotyledons, leaves, and stems. In this mutant condition, anthocyanin may or may not be expressed.
In this exercise, you will carry out a dihybrid cross between No Purple (anthocyaninless), Yellow-Green Plants and Purple (anthocyanin present), Green Plants. Genotypically, this cross looks like this: anl/anl, ygr/ygr X anl/ANL, ygr/YGR. Before you begin this experiment, you will formulate a Hypothesis for the mode of inheritance of these traits, egs., simple Mendelian dominance and recessiveness, intermediate dominance, or another non-Mendelian mode of inheritance. You must also Predict the results of this cross based on your hypothesis. An outline of your cross in the form of a Punnett Square is also expected, revealing the genotypic and phenotypic ratios of the progeny. All of this must be written up in a Protocol.
Key: You need not write up two separate Protocols. You can write up one composite Protocol which differentiates between the two experiments that are assigned, ie., their separate Hypotheses and Predictions must be stated.
Remember, your composite Protocol is due on
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