Datura stramonium (the Jimsonweed) expresses flower colors of pur...

Question

Datura stramonium (the Jimsonweed) expresses flower colors of purple and white and pod textures of smooth and spiny. The results of two crosses in which the parents were not necessarily true breeding are shown below.

Based on these results, put forward a hypothesis for the inheritance of the purple/white and smooth/spiny traits.

Accepted Answer

Hey everyone. Let's take a look at this question together when two independent events are occurring simultaneously. Like in a di hybrid cross and the ratio of each joint phenotype in combination can be calculated by multiplying their individual probabilities. This statement is true for what? So what do we mean by two independent events that are occurring simultaneously? Well, let's go ahead and set up an example. So we're talking about a plant and maybe we want to find out the probability of this P plant being both yellow and wrinkled. And so let's say we have yellow which is big Y. Or green which is little Y. With the color yellow being the dominant allele. And then for wrinkled we'll have a big R. And then for maybe around we'll have a little R. And wrinkled is also the dominant allele. So we would set up opponent square for the color. So we have big y. Little Y. Let's go ahead and say big y. Little Y. And so a probability of it being yellow we could say for this specific example is 123 out of four. So 3/4 probability of it being yellow. And so let's set up an example for wrinkled around our little R. Big r. Little r. Little R. And so we have two that are wrinkled. So that would be one out of two. And so to find the probability of it being yellow and wrinkled. We would take that 3/4 which is the probability of the p plant being yellow and multiplied by that one half. Which is the probability of the p plant being wrinkled. And so then we would end up with 3/8 because when we have those two independent events that are occurring at the same time, which in this case we're trying to figure out the probability of a pea plant that would be yellow and wrinkled and find out the probability that the plant would be yellow and find the probability that the plant will be wrinkled. And then we multiply those two probabilities together. And so this is what's called the product rule or answer choice B. Because the product rule is when you have two independent events occurring at the same time and then you multiply the ratio of each joint fanatic combination to get that combined probability of having that species B. In this case yellow and wrinkled. So answer choice B is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

Key Concepts

Mendelian Inheritance

Phenotype and Genotype

Punnett Square

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