Steps to Performing a Test Cross

by Jason Amores Sumpter
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in this video, we're going to talk about the steps to performing a test cross. And so let's say that we have a yellow pea plant, but we're not sure what the Gina type is of this yellow pea plant. Maybe this yellow pea plant has a homeless, I guess. Dominant Gina type. But maybe this yellow plant has a hetero zegas Gina type. How do we figure that out? Well, we need to perform a test cross. And so there are really three steps when it comes to performing a test cross and notice that Step three also has a part three a and three beat. And so the very first step in performing a test crosses to cross the mystery parent with the unknown Gina type with a homo zegas recess it parent. Then the second step of performing a test cross is to analyze the babies of the cross or, in other words, to analyze the offspring FINA types and then the third and final step of performing the test crosses to make a conclusion about the mystery parents Gina type. Based on the results, if all of the babies or all of the offspring had the dominant phenotype, then that means that the mystery parents genotype must be home, a zegas dominant or to capital wise. But if the offspring of the cross showed mixed offspring with mixed FINA types, then that must mean that the mystery parents Gina type is hetero zegas, meaning it has one dominant alil and one lower case or recess of Alil. And so let's take a look at our example down below to see how this test cross exactly works to determine the Gina type of this mystery parent, this yellow p. And so notice that over here on the left hand side and on the right hand side, we're showing you this mystery parent. And of course, we know that it is yellow, but we don't know what it's Gina type is. We know that it has at least one dominant alil, but is it going to be homeless, I guess Dominant or hetero? Zegas? Well, what we need to do is the very first step, again is to cross the mystery parent with the homeless, I guess, recess of Parent and so notice that in both situations we're taking the mystery parent and we're crossing the mystery parent with a Hamas, I guess. Recess, if, parent. And then what we need to do is analyze the results of the babies. If all of the babies come out 100% with the dominant phenotype of yellow, then that must mean if we trace this, uh, backwards to see the possible results of the offspring, we know that they must have at least one dominant Aaliyah, one capital. Why? And that must mean that the gammy must have had a capital y here as well. And that must mean that the mystery parent is Homo Zegas dominant. And so if all of the offspring 100% of the offspring show the dominant phenotype that they're yellow piece as we sit here, all dominant offspring means that the mystery parents Gina type is Homo zegas dominant to capitalize. But let's say that there is a mixture of FINA types in the offspring where 50% of the offspring are showing the dominant trait of yellow piece. But the other 50% of the offspring are showing the recess Ivo trait for Greenpeace. Then of course, that must mean that half of these, uh, here must be, um homo zegas recessive having to lower case wise. And, of course, they must have gotten this lower case. Why from one of the fathers game it's. And that means that the mystery parent must have a home hetero six genotype. And so again, if you see mixed offspring, that means that the mystery parents genotype is hetero zegas. And so you can see that just by analyzing the results, do we see mixed offspring or do we see ah, 100% dominant? Uh, the 100% of the offspring showing the dominant tree and depending on that well, you either figure out that the mystery parent was home a zegas dominant or if there was a mixed that the mystery parent is hetero zegas. And that's how you determine the Gina type of the mystery parent by performing a test cross. And so this year concludes our introduction to how to perform a test cross, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video