Warm Up Exercise: Hypotheses and Predictions
You can practice with hypotheses and predictions with the scenarios on this page. The warm-up exercises are for your own notes and to help you with the rest of the lab; you will not be submitting them with the lab assignment itself.
Scenario 1
Assume that fur colour in cats is associated mainly with a single gene with two alleles, G and g. Your hypothesis is that grey fur colour is dominant over orange fur colour. Your experiment is to cross two cats of known genotype Gg. Use a Punnett square to generate a testable prediction: what phenotypic ratio is expected from this experiment, if your hypothesis is correct? Remember that the Punnett square is not the prediction itself, because you are not able to observe genotypes directly - the Punnett square is a tool that allows you to generate a prediction from a given hypothesis and experiment.
Print this page or sketch the table below in your notes and fill it in to make your Punnett square. (You many not necessarily need to fill all the cells in the table.) After completing the Punnett square, state your prediction in a single sentence.
(5x5 table)
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Scenario 2
Now let's consider an additional character in cats: fur length. Short fur (F) is dominant over long fur (f). Two parents, both of genotype GgFf, are crossed and the offspring phenotypes are observed.
What is the full hypothesis for this scenario (taking into account that information from Scenario 1 is also relevant)? What is the experiment?
Use a Punnett square to generate a testable prediction for the outcome of this experiment if the hypothesis is correct. After completing the Punnett square, state your prediction in a single sentence.
(5x5 table)
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Scenario 3
In this lab, you will be studying the genetics of corn. For this scenario, assume that purple colour is dominant over yellow colour in corn kernels.
You find some corn plants growing on the edge of a field. All of the kernels of corn on these plants are purple, and you take one of these kernels and grow it into a mature corn plant. Is this plant true breeding for the purple colour, or is it a hybrid? You decide to cross this plant with a true-breeding yellow kernel corn plant to find out.
Choose letters to represent the alleles in this scenario. What is your hypothesis about the genotype of the purple kernels? Fill in the blank in the statement below by using a Punnett square to generate a prediction.
IF [your hypothesis] is correct, AND a purple corn plant is crossed with a yellow corn plant [the experiment], THEN the resulting offspring should have an observable phenotypic ratio of __________________.
Check your Punnett square and prediction.